Here are my notes on Michael Daley's presentation on moving to 3D.
A subject that scares the heck out of everybody.
Can do an awful lot without being a genius.
Http://71squared.com
Book: "learning ios game programming"
http://Particledesigner.71squared.com
Sample code is not optimized, for clarity, but still gets good performance.
Prototype project http://tiny url.com/28jp4pm
A turret game - play around with it!
One of first things you need to do to the opengl template is to ad a depth buffer. Added to createframebuffer method. (remove it in delete frame buffer method, too.)
Next must setup the perspective projection to td3dviewcontroller.mm in initOpenGLES1. Then set up the model view matrix. Setup light, fog, etc. In same method.
The math - don't need to be a math or physics genius. But you do need to have some basics, vectors, points, dot produce, cross product, normal. But the work has been done and coded in classes: SSvectorUtil.h,SSMatrixUtil.h
(found in matrix & vector folder in project, if you're curious.)
--------
State management in OpenGL
It will set a state even if the new value is the same as the old. Perhaps encapsulate the OpenGL state machine, which is what Michael has done with OGLState class.
--------
Creating 3d models
Blender. (free)
Jeff lamarche's blog has a great exporter for blender.
Blender can unwrap the shape (to a UV image) or can let you paint the vertices. Export to a png image. Then export the vertices and normals.
Each model's geometry, normal &texture data is loaded into static Vertex buffer objects.
Each model's text is created as an instance of Texture2D
Reuse models and textures where you can.
Michael has created an AssetManager class that keeps track of all these reusable assets.
(A Mipmap contains several images of the same thing that are prescaled down.)
Collisiiion detection - hard to do fast in 3d. But it has been solved. See bullet3d physics engine. (free) put out by a guy at Sony.
When we create an object, we set up it's physics object. In missile.mm class, for instance, initPhysics() method sets up the model for its physics.
Then in the viewcontroller run its initphysics() method. Also sets up a mo course collision detection shape for things - only checks the "tight" collision mesh if the course one has a collision.
Then in the view controller's game loop (update with delta) calculate the physics. Make sure that the physics update is not directly synched to the screen refresh rate.
------
Setting up the camera
To draw objects, you really are moving the world around to center the objects location and drawing it "here" then moving the world to the next object. Then you move the world to center on where the camera is and set it "here."
Ship class - found Internet code on "autonomous steering."
--------
Moving around
When set up game, set up core motion - reads the gyro 1/60 sec. Then in drawFrame method, get the attitude from the gyro and then applying that matrix to the model view.
Q&A: memory management : recommends caching the model. There is no hard/fast rule. Just kept a pool of allocated objects ahead of time and reused over and over again.
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Sunday, October 17, 2010
#VTM_iPhone notes on using cocos2d for game development
Here are my notes on the "Using Cocos2D for Game Development" presentation by Rod Stougo
He has a book coming out soon.
Cocs2dbook.com
Free!
OpenGL es rendering and performance without having to learn OpenGL es to get started.
(you get access to full source code)
Www.cocos2d-iPhone.org/download
Recommends the unstable version
Sudo ./install-templates
This puts templates into Xcode. Box2d is physics engine, so is chipmunk.
Comes with two sample programs, for Mac games and ios games.
Lots of samples. Make sure you select both active target and active executable.
Uses a movie metaphor - scenes, director, layers. (ok, the actors are called sprites.)
Z-layers are compositing order, and there are z-values for the objects within the layers.
Layers can subscribe to touch and accelerometer events
Actions are an easy way to apply transitions, effects and animations to the sprites
Moveto, move by,scale by, scale to, fadein, fadeout, rotate,....
Ccsequence combines actions sequentially, ccspawn combines actions simultaneously
Change gears: Optimization
Starting to get complicated sending info if you send images one at a time - make a sprite sheet. Aka a "texture atlas" zwoptex online sprite sheet creator.
Physics engines box2d and chipmunk(newer) pretty similar. Box is c++, chipmunk is c. Wrapped in objc. If you use c++ code, implementation files must have .mm suffix for complier.
Cocsdenshion sound engine- wrapper for Avaudiiplayer and openAL
Simple, synchronous and asynchronous, background and sound effects
Particle systems!
Cocos2dbook.com
Physics world with a graphics world on top. Calculates where the objects are and then moves the graphics on where they should go. The sprite doesn't have any physics logic.
Event handlers: cctouchesbegan
To make the snowballs, find where the touches start and end and find the delta. Create physics object, and create force or impulse. Add a small rotation
Collisions have masks to indicate which things have detectable collisions.
Can animate the appearance of sprites easily
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He has a book coming out soon.
Cocs2dbook.com
Free!
OpenGL es rendering and performance without having to learn OpenGL es to get started.
(you get access to full source code)
Www.cocos2d-iPhone.org/download
Recommends the unstable version
Sudo ./install-templates
This puts templates into Xcode. Box2d is physics engine, so is chipmunk.
Comes with two sample programs, for Mac games and ios games.
Lots of samples. Make sure you select both active target and active executable.
Uses a movie metaphor - scenes, director, layers. (ok, the actors are called sprites.)
Z-layers are compositing order, and there are z-values for the objects within the layers.
Layers can subscribe to touch and accelerometer events
Actions are an easy way to apply transitions, effects and animations to the sprites
Moveto, move by,scale by, scale to, fadein, fadeout, rotate,....
Ccsequence combines actions sequentially, ccspawn combines actions simultaneously
Change gears: Optimization
Starting to get complicated sending info if you send images one at a time - make a sprite sheet. Aka a "texture atlas" zwoptex online sprite sheet creator.
Physics engines box2d and chipmunk(newer) pretty similar. Box is c++, chipmunk is c. Wrapped in objc. If you use c++ code, implementation files must have .mm suffix for complier.
Cocsdenshion sound engine- wrapper for Avaudiiplayer and openAL
Simple, synchronous and asynchronous, background and sound effects
Particle systems!
Cocos2dbook.com
Physics world with a graphics world on top. Calculates where the objects are and then moves the graphics on where they should go. The sprite doesn't have any physics logic.
Event handlers: cctouchesbegan
To make the snowballs, find where the touches start and end and find the delta. Create physics object, and create force or impulse. Add a small rotation
Collisions have masks to indicate which things have detectable collisions.
Can animate the appearance of sprites easily
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#VTM_iPhone notes on game center talk
My notes on the game center talk by Jessica Kahn.
Social gaming functionality, provided by apple
- authentication
-leader boards
Achievements
Friendsinvitations and matchmaking
P2p networking
And one other.
Ios 4.1+
Game center is just catching on.
Why bother? Lots of competition, but game center is a free way to raise visibility. Also, game center advertises what your friends are playing, even if you don't own them. Friends can invite you to games you don't own.
Competing solutions: Plus+, OpenFeint, ScoreLoop, Crystal, and 3rd party
Tapulous network (jessica's company) has some things that apple doesn't, some things it does, but lacks some that apple does.
Bundle identifier, game kit linkage, view controller-based user interface, Ability to code with blocks
BundleID (eg. Com.tapulous.gamecenterdemo)
Best to do a weak link, checking for game kit and ios4.1 or later on user's phone
Leaderboards, achievements, and matchmaking all use view controller subclases for their UI.
GameKit often takes blocks as parameters.
The Basics:
Authentication, leader boards, achievements
Auth... Do it as soon as your app can display ui. One line of code, with a block as error handler, triggers a welcome back overlay at top of screen.
With multitasking, might log out while you are in background. Be observer for GKPlayerAuthenticationDidChange
-----> supporting authentication is enough to get the exposure benefits of game center!
Leaderboards
Configure in iTunes connect
Report using GKscore
Display using GKLeaderboardViewController
Or
get the data from the game sever and display, yourself
Reporting - if it fails, stash the data locally, and try again soon. Don't need to tell user, according to apple interface design.
Leaderboards show up in game center, even if you don't display them in your app.
Achievements are just like leaderboards.
--------
Bonus points
(I had to step out, so much of this is omitted)
Matchmaking - came back in the middle. Looks a bit complicated. But then, romance usually is.
Suggested: doing a lot at boot time - but watch out about interfering with user experience.
Peer-to-peer networking
High-level interface.
Start by making the match (see above)
Decide which data to transmit - as little and as rarely as you can.
You can transfer data reliably or unreliably. Send data to all players or to one specific user.
Data must be "byte (sic) sized" (sic)
Read up on two GKMatch methods
SendDataToAllPlayers...
Voice chat
Use GKVoiceChat & GKMatch
First create and make active a playAndRecord AVAudioSession
Then create one or more voice channels using voiceChatWithName
Start and stop ability to talk with methods on GKVoiceChat.
-------
Gotchas
Fragmentation, due to unsupported os versions.
Complexity, if game is OpenGL based
Beware flaky networks!
Prevent cheaters, you can't reset a leaderboard.
- if you are storing scores, save it in a way so that people can't read it.
Invitation handlers can happen at inopportune times.
Network activity can hamper in-game fps and audio performance.
Great questions, but I was distracted by q/a and did not write them down. Some on age-appropriateness, some on testing, some on handling the modality of authentication requests.
She's vp of engineering Disney mobile and is "hiring like crazy"
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Social gaming functionality, provided by apple
- authentication
-leader boards
Achievements
Friendsinvitations and matchmaking
P2p networking
And one other.
Ios 4.1+
Game center is just catching on.
Why bother? Lots of competition, but game center is a free way to raise visibility. Also, game center advertises what your friends are playing, even if you don't own them. Friends can invite you to games you don't own.
Competing solutions: Plus+, OpenFeint, ScoreLoop, Crystal, and 3rd party
Tapulous network (jessica's company) has some things that apple doesn't, some things it does, but lacks some that apple does.
Bundle identifier, game kit linkage, view controller-based user interface, Ability to code with blocks
BundleID (eg. Com.tapulous.gamecenterdemo)
Best to do a weak link, checking for game kit and ios4.1 or later on user's phone
Leaderboards, achievements, and matchmaking all use view controller subclases for their UI.
GameKit often takes blocks as parameters.
The Basics:
Authentication, leader boards, achievements
Auth... Do it as soon as your app can display ui. One line of code, with a block as error handler, triggers a welcome back overlay at top of screen.
With multitasking, might log out while you are in background. Be observer for GKPlayerAuthenticationDidChange
-----> supporting authentication is enough to get the exposure benefits of game center!
Leaderboards
Configure in iTunes connect
Report using GKscore
Display using GKLeaderboardViewController
Or
get the data from the game sever and display, yourself
Reporting - if it fails, stash the data locally, and try again soon. Don't need to tell user, according to apple interface design.
Leaderboards show up in game center, even if you don't display them in your app.
Achievements are just like leaderboards.
--------
Bonus points
(I had to step out, so much of this is omitted)
Matchmaking - came back in the middle. Looks a bit complicated. But then, romance usually is.
Suggested: doing a lot at boot time - but watch out about interfering with user experience.
Peer-to-peer networking
High-level interface.
Start by making the match (see above)
Decide which data to transmit - as little and as rarely as you can.
You can transfer data reliably or unreliably. Send data to all players or to one specific user.
Data must be "byte (sic) sized" (sic)
Read up on two GKMatch methods
SendDataToAllPlayers...
Voice chat
Use GKVoiceChat & GKMatch
First create and make active a playAndRecord AVAudioSession
Then create one or more voice channels using voiceChatWithName
Start and stop ability to talk with methods on GKVoiceChat.
-------
Gotchas
Fragmentation, due to unsupported os versions.
Complexity, if game is OpenGL based
Beware flaky networks!
Prevent cheaters, you can't reset a leaderboard.
- if you are storing scores, save it in a way so that people can't read it.
Invitation handlers can happen at inopportune times.
Network activity can hamper in-game fps and audio performance.
Great questions, but I was distracted by q/a and did not write them down. Some on age-appropriateness, some on testing, some on handling the modality of authentication requests.
She's vp of engineering Disney mobile and is "hiring like crazy"
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Ow... Sore brain. #VTM_iPhone
So here it is, the morning of the second day of the "Voices that Matter" iPhone conference. (way better than the "Irrelevant Noise" convention.)
My brain is sore. It was a very long - but inspiring - day yesterday, and we just heard a great keynote from a guy dressed as a pirate talking about not sucking. I'm looking forward to a series of great talks about stuff I'm really interested - and I hope that I'll be able to absorb it all. I need time to reflect, to tinker, to play, but I also want to be ready for the next great talk, to cleanse the palette, so to speak.
Oops. The next talk is starting!
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My brain is sore. It was a very long - but inspiring - day yesterday, and we just heard a great keynote from a guy dressed as a pirate talking about not sucking. I'm looking forward to a series of great talks about stuff I'm really interested - and I hope that I'll be able to absorb it all. I need time to reflect, to tinker, to play, but I also want to be ready for the next great talk, to cleanse the palette, so to speak.
Oops. The next talk is starting!
- Posted using BlogPress from my iPad
Saturday, October 16, 2010
#VTM_iPhone notes on STAssertTrue
Here are my notes on Graham Lee' unit testing presentation. Note: coming into this, I have heard of unit testing and have a general idea of what it means, but I have never seen it done. I presume it means to do an automated process of running a method with different data sets and checking that the answer is what you wanted each time. Probably, it includes boundary cases, but I don't know.
Software engineering goals: make money (sometimes)... By making something that the user wants. - meets their requirements, without being too expensive.
Testing isn't about finding bugs - it's about validating that your code does what it should., finding bugs is a secondary effect.
The earlier a bug is introduced, the more it costs if you find it late. Unit testing helps with the design and build aspects reducing errors.
Undirected unit testing - checking the minutiae of the program, the opposite side from external testing by somebody who doesn't know the program I.e., the user.
test driven development:
*black-box thinking for the developer.
*YAGNI you ain't gonna need it. Only write the code you need.
*Avoid regression bugs. Keep the tests around, so later code doesn't break earlier code without your knowledge.
*assists accurate planning
Find bugs before....
...your customers do.
Zune didn't know about leap year. Ah, they're incredibly rare.
TDD != [bullet silverColor]
you can't assume the developer understood the problem...or that the requirements didn't change, and it doesn't guarantee successful integration
Takes time to write tests, and you actually run them.
How TDD works: RED - GREEN - REFACTOR
What do I test? Anything within reason - time, environmental conditions (ie DBs, filesystem, network - not repeatable)
Evaluate risk - known buggy code, heavily used code, tricky problems
When do I test? At any change, plus before release.
Testable code: short classes with short methods, each with obvious effects, few & predictable side effects, with helper data passed in - not discovered, low "cyclomatic complexity" - don't need to test thousands of combinations.
This means the end of a @interface GodView:UIViewController
OCUnit and XCode3 or XCode4
GHUnit ... Better than OCUnit? (Does it run on the iPod, itself?-HH)
plug of kaleidoscope app?
Fakes and mocks? Fake is dummy input data, and mock is dummy local data, I think.... - HH
Recommends "refactoring: improving the design of existing code", "test-driven development"(Kent beck), "test-driven development: a practical guide", "xUnit test Patterns", et al
Iamleeg at the usual sites, twitter, etc.
Note: I know more than I did, but I still don't know enough that I am ready to go out and start unit testing. A lot of theory here, but I probably needed a more practical demonstration.
- Posted using BlogPress from my iPad
Software engineering goals: make money (sometimes)... By making something that the user wants. - meets their requirements, without being too expensive.
Testing isn't about finding bugs - it's about validating that your code does what it should., finding bugs is a secondary effect.
The earlier a bug is introduced, the more it costs if you find it late. Unit testing helps with the design and build aspects reducing errors.
Undirected unit testing - checking the minutiae of the program, the opposite side from external testing by somebody who doesn't know the program I.e., the user.
test driven development:
*black-box thinking for the developer.
*YAGNI you ain't gonna need it. Only write the code you need.
*Avoid regression bugs. Keep the tests around, so later code doesn't break earlier code without your knowledge.
*assists accurate planning
Find bugs before....
...your customers do.
Zune didn't know about leap year. Ah, they're incredibly rare.
TDD != [bullet silverColor]
you can't assume the developer understood the problem...or that the requirements didn't change, and it doesn't guarantee successful integration
Takes time to write tests, and you actually run them.
How TDD works: RED - GREEN - REFACTOR
What do I test? Anything within reason - time, environmental conditions (ie DBs, filesystem, network - not repeatable)
Evaluate risk - known buggy code, heavily used code, tricky problems
When do I test? At any change, plus before release.
Testable code: short classes with short methods, each with obvious effects, few & predictable side effects, with helper data passed in - not discovered, low "cyclomatic complexity" - don't need to test thousands of combinations.
This means the end of a @interface GodView:UIViewController
OCUnit and XCode3 or XCode4
GHUnit ... Better than OCUnit? (Does it run on the iPod, itself?-HH)
plug of kaleidoscope app?
Fakes and mocks? Fake is dummy input data, and mock is dummy local data, I think.... - HH
Recommends "refactoring: improving the design of existing code", "test-driven development"(Kent beck), "test-driven development: a practical guide", "xUnit test Patterns", et al
Iamleeg at the usual sites, twitter, etc.
Note: I know more than I did, but I still don't know enough that I am ready to go out and start unit testing. A lot of theory here, but I probably needed a more practical demonstration.
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#VTM_iPhone notes on multitasking presentation
Here are my notes on jeff lamarche's presentation, "multitasking the iPhone sdk way"
One of the biggest complaints from developers about early ios.
Actually, it had multitasking from day one - lots of first party apps running once.
Of course, apple just does this to be mean.
Real reason - battery impact and foreground application responsiveness
The audience at this convention - we're the outliers. Most people see computers as an obstacle.
"Devices for the rest of us."
Myth: with ios 4, we have "true multitasking." but don't use it for its own sake if you don't really need them. Will a push notification work?
Basically, you can maintain state, and can't do much (if any) processing in background.
Legacy apps can be set to opt out of multitasking. In info.plist.
Four types of background tasks - background audio, voip, navigation & location tracking, task completion
Playing nicely: application lifecycle
Before 4.0: not running, inactive, active
application delegate fires when state changes
Active --> inactive: applicationWillResignActive
Active ->not running: applicationWillTerminate
At 4.0:
States
foreground: active, inactive
Background: suspended, active
Not running
If you want to keep running in background, keep your (over)head low.
ApplicationDidEnterBackground
ApplicationWillEnterForeground
Problem: if you are in background, will not get notification if the program is killed. Issues for persistence.
--------
Background
Should not run code that does drawing or leverages the gnu
Should close any network listeners
Stop advertising or looking for bonjour services
But make sure you resume when you return tho the foreground
Generally, should dismiss alerts, action sheets.
If multiple buttons, pick the non-destructive option.
Background - hide sensitive info in UI
Shouldn't access shared data APIs - calendar, address book, music/media library
Hint: instruments works fine with background applications - in fact, a very good idea.
You can still set base SDK to 4.x and still target 3.0. Delegate methods just don't get called.
Don't check hardware or OS version!
Task completion API - general purpose. Can request to keep running - to finish a process. Must finish in given time limit, or will be killed. You do have a chance to clean up and save.
How long? Not documented. Simulator gives 5 minutes. You don't have to wait for app event to request time.
See handout for sample code.
Uses blocks.... Get over it, and they are coming. Suddenly, they will click.
Nb: if it's long enough to require task completion, it needs to be off the main thread.
Background audio
It's opt-in. Must identify that you use them in your info.plist file
Your background app will override foreground audio!
Background apps using radios can drain battery. Be sure to close down the connection.
The background audio can also record sound!
Must implement avaudiosessiondelegate - should implement begin interruption and end interruptooonwithflags
In, must override canBecomeFirstResponder to return YES.
Apple has put a lot of thought about this. Balance between developers and users.
If you can't find a way around this: bugreport.apple.com
Stop drawing? Mostly automatic. You do (seem) to get some time after the notification arrives that the app will go inactive
Jeff_lamarche@Mac.com
- Posted using BlogPress from my iPad
One of the biggest complaints from developers about early ios.
Actually, it had multitasking from day one - lots of first party apps running once.
Of course, apple just does this to be mean.
Real reason - battery impact and foreground application responsiveness
The audience at this convention - we're the outliers. Most people see computers as an obstacle.
"Devices for the rest of us."
Myth: with ios 4, we have "true multitasking." but don't use it for its own sake if you don't really need them. Will a push notification work?
Basically, you can maintain state, and can't do much (if any) processing in background.
Legacy apps can be set to opt out of multitasking. In info.plist.
Four types of background tasks - background audio, voip, navigation & location tracking, task completion
Playing nicely: application lifecycle
Before 4.0: not running, inactive, active
application delegate fires when state changes
Active --> inactive: applicationWillResignActive
Active ->not running: applicationWillTerminate
At 4.0:
States
foreground: active, inactive
Background: suspended, active
Not running
If you want to keep running in background, keep your (over)head low.
ApplicationDidEnterBackground
ApplicationWillEnterForeground
Problem: if you are in background, will not get notification if the program is killed. Issues for persistence.
--------
Background
Should not run code that does drawing or leverages the gnu
Should close any network listeners
Stop advertising or looking for bonjour services
But make sure you resume when you return tho the foreground
Generally, should dismiss alerts, action sheets.
If multiple buttons, pick the non-destructive option.
Background - hide sensitive info in UI
Shouldn't access shared data APIs - calendar, address book, music/media library
Hint: instruments works fine with background applications - in fact, a very good idea.
You can still set base SDK to 4.x and still target 3.0. Delegate methods just don't get called.
Don't check hardware or OS version!
Task completion API - general purpose. Can request to keep running - to finish a process. Must finish in given time limit, or will be killed. You do have a chance to clean up and save.
How long? Not documented. Simulator gives 5 minutes. You don't have to wait for app event to request time.
See handout for sample code.
Uses blocks.... Get over it, and they are coming. Suddenly, they will click.
Nb: if it's long enough to require task completion, it needs to be off the main thread.
Background audio
It's opt-in. Must identify that you use them in your info.plist file
Your background app will override foreground audio!
Background apps using radios can drain battery. Be sure to close down the connection.
The background audio can also record sound!
Must implement avaudiosessiondelegate - should implement begin interruption and end interruptooonwithflags
In, must override canBecomeFirstResponder to return YES.
Apple has put a lot of thought about this. Balance between developers and users.
If you can't find a way around this: bugreport.apple.com
Stop drawing? Mostly automatic. You do (seem) to get some time after the notification arrives that the app will go inactive
Jeff_lamarche@Mac.com
- Posted using BlogPress from my iPad
#VTM_iPhone notes on around the block with blocks talk
Here are my notes on Bob Clair's "around the block with blocks" talk
I feel kind of foolish about this - I hadn't heard about blocks until today, so I'm glad I'm here for this presentation.
He says there are some typos in original presentation posted , but new one is forthcoming.
Blocks are not in ios3.2 ( which would explain why I haven't heard of them.)
What problem are we trying to solve. How to package up some functionality (some code to be executed) to pass on to somebody else.
In other languages, called "closures" or "anonymous functions"
Blocks are an apple addition to C, objectiveC, c++
New in snowleopard and ios4
Diversion 1: functions calls are jumps, which you can make dynamic by using a pointer to a function.
(ugly) Example: Void (*myFunctionPtr)(int)
See PowerPoint for code with example. Too much to type!
Main use of a function pointers is for callbacks. (hooks? -hh)
This stuff works, but it's a pain in the butt, particularly when passing lots of data.
You can also do this with selectors SEL objects.
Diversion#2: nsinvocation
Bundles up (freeze dries) receiver, method and arguments. Then the invocation can be interrogated to find the return value.
More ugly code as example in PP...
The issue is that these things are a royal pain to set up.
Blocks:
^(arg list) {body};
No return type declared. This is a block literal.
There is no name for this it is anonymous.
A trivial example.
^(int n) {return n*2;};
How do you call this?
Int j = ^(int n) {return n*2;}(9);
But this is dopey. Send it to a block variable.
Declare a variable that is a pointer to a block
Return type (^myBlock. Afasdhjohfoafhgkj
Int (^doubler)(int);
Doubler = ^(int){return n*2;};
Too fast to keep up. See pp.
Funny syntax when trying to pass a block as a function argument.
So what is the big deal?!?
A block has read only access to automatic variables visible in it's enclosing scope! <-------
When you declare the block, it freezes the value of any extra-scope variables it references in the block. The variable is copied into a structure with all the ?
The block is created on the stack, not the heap. Blocks have same lifetime as an automatic variable (local variable?) when the block literal goes out of scope, it is undefined.
A block variable is declared with type edifier __block
__block int myBlockInt
Can be read/write by a block in the near by scope.
Under the hood.
Blocks are actually objectivec objects
Only example of stack based objectivec
A private subclass of nsobject
The header isn't provided so you can't subclass them or monkey around with them.
Passing a block into a function as an argument is safe, in a single thread.
What if you want to pass the block to another thread or pass it back out of a function to use later?
To do this, you must... Copy the block. He mentioned some c methods, but I'm just listing objc techniques here.
In objc, use the [. Copy] method on the block, since it descends from nsobject. The copied block goes to the heap, and moves any __block variables and fixes any links to those variables. ( mostly works)
Memory management in objc, remember doing copy requires a release or autorelease.
Some uses for blocks: collection classes, animation, threading, completion handlers
Also useful in grand central dispatch - give GCD blocks to run for you.
Gripes: 1) block is a word already in use 2) smashes encapsulation 3) function oriented, not object oriented 4) encourages Design Your Own Language Syndrome
Plug the book "Learning Objective-C 2.0" by Robert Clair. This is chapter 16.
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I feel kind of foolish about this - I hadn't heard about blocks until today, so I'm glad I'm here for this presentation.
He says there are some typos in original presentation posted , but new one is forthcoming.
Blocks are not in ios3.2 ( which would explain why I haven't heard of them.)
What problem are we trying to solve. How to package up some functionality (some code to be executed) to pass on to somebody else.
In other languages, called "closures" or "anonymous functions"
Blocks are an apple addition to C, objectiveC, c++
New in snowleopard and ios4
Diversion 1: functions calls are jumps, which you can make dynamic by using a pointer to a function.
(ugly) Example: Void (*myFunctionPtr)(int)
See PowerPoint for code with example. Too much to type!
Main use of a function pointers is for callbacks. (hooks? -hh)
This stuff works, but it's a pain in the butt, particularly when passing lots of data.
You can also do this with selectors SEL objects.
Diversion#2: nsinvocation
Bundles up (freeze dries) receiver, method and arguments. Then the invocation can be interrogated to find the return value.
More ugly code as example in PP...
The issue is that these things are a royal pain to set up.
Blocks:
^(arg list) {body};
No return type declared. This is a block literal.
There is no name for this it is anonymous.
A trivial example.
^(int n) {return n*2;};
How do you call this?
Int j = ^(int n) {return n*2;}(9);
But this is dopey. Send it to a block variable.
Declare a variable that is a pointer to a block
Return type (^myBlock. Afasdhjohfoafhgkj
Int (^doubler)(int);
Doubler = ^(int){return n*2;};
Too fast to keep up. See pp.
Funny syntax when trying to pass a block as a function argument.
So what is the big deal?!?
A block has read only access to automatic variables visible in it's enclosing scope! <-------
When you declare the block, it freezes the value of any extra-scope variables it references in the block. The variable is copied into a structure with all the ?
The block is created on the stack, not the heap. Blocks have same lifetime as an automatic variable (local variable?) when the block literal goes out of scope, it is undefined.
A block variable is declared with type edifier __block
__block int myBlockInt
Can be read/write by a block in the near by scope.
Under the hood.
Blocks are actually objectivec objects
Only example of stack based objectivec
A private subclass of nsobject
The header isn't provided so you can't subclass them or monkey around with them.
Passing a block into a function as an argument is safe, in a single thread.
What if you want to pass the block to another thread or pass it back out of a function to use later?
To do this, you must... Copy the block. He mentioned some c methods, but I'm just listing objc techniques here.
In objc, use the [. Copy] method on the block, since it descends from nsobject. The copied block goes to the heap, and moves any __block variables and fixes any links to those variables. ( mostly works)
Memory management in objc, remember doing copy requires a release or autorelease.
Some uses for blocks: collection classes, animation, threading, completion handlers
Also useful in grand central dispatch - give GCD blocks to run for you.
Gripes: 1) block is a word already in use 2) smashes encapsulation 3) function oriented, not object oriented 4) encourages Design Your Own Language Syndrome
Plug the book "Learning Objective-C 2.0" by Robert Clair. This is chapter 16.
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#VTM_iPhone notes on memory management talk
Here are my notes on Steve Kochan's talk on "Really, really understanding memory management"
Steve@classroomM.com
Twitter: @skochan
Founder of classroom.com, author
Objectives: to really understand different memory maNagement strategies, et al
Three memory management strategies: automatic garbage collection, autorelease pool, manual allocate. And release of objects
Garbage collection not avail on ios-
RAM space ranges from 128-512 mb on ios objects, but count on much less available. There's no memory paging.
Autorelease pool is created at start of main and drained at the end of main
For cocoa and ios apps, automatically drained at end of event cycle
Multithread apps need separate pools per thread.
Framework objects are (mostly) autoreleased.
Doing example with a fraction class too much to take notes here.
Alloc involves retain - must be released.
If you release the single retained object twice (over released) error message says "released freed object"
Dealloc - never called directly, of course.
Retain count: how many people have dibs on this object?
When retain count hits zero, system invokes dealloc...
Autorelease doesn't affect retain count, but when pool is drained, the object will be released (once). The "pool" isn't a space where objects are stored - it is a list of objects that should be released when you drain the pool.
When is the pool released? Other than when you specifically tell it to? At end of event loop.
Retaining allows objects to survive after the pool is drained... From one event loop to the next.
When you add an object to an array, it sends a retain to the object. True for most methods that have "add" or "replace" in method name.
Methods with "remove" in name will release.
You can have local autorelease pool, even nested ones.
Alloc, copy*, or new must manually maintain
Autoreleased methods: static methods that return objects e.g. [nsmutabledictionary dictionary] returns an autoreleased object.
[[nsmutabledictionary alloc] init] is not autoreleased. Both have been retained once.
Trouble example: add a view to a superview and release it. Later in program, remove from superview - the view is deallocated.
Strange optimizations: constant string objects and nsnumber objects from -1 to 12 are often higher than they "should" be.
If you don't need an object in a method but are going to return it, now is a good time to autorelease.
Event cycle:
Remember that a new autorelease pool gets created when your app is to process an event. The pool gets drained when that method is done. Event is pressing a button, dragging, etc.
Example of trouble: in viewdidload method, user has said data = [nsarray array] -- it gets deleted at end of view loading event!
Could retain, could use alloc/init, or use synthesized setter method, which retains. ****But don't want to alloc AND use synthesized setter- that double retains! Causes a memory leak****
If you use @property (retain), then setter involves retaining. @property(assign) doesn't retain.
Another example: when you initWithCoder, the stuff in the coder is autoreleased, so you better do something that retains the data!
@property (copy) always makes an immutable copy, not a mutable one, even if the instance variable is of a mutable type.
When memory gets low in iPhone:
Application did receive memory warning
Release data you don't need!
Didreceivememorywarning is sent to all view controllers.
By default, views will be released if not in a superview
When view is released, viewdidunload is sent to the viewcontroller
Finding memory leaks
Put breakpoint or slog in dealloc
Use static analyzer- build and analyze puts blue icons in bak point bar. Click on blue boxes for more and more helpful info! Very neat!
Instruments - get guide from apple's website
More resources on PowerPoint that Steve posted.
- Posted using BlogPress from my iPad
Steve@classroomM.com
Twitter: @skochan
Founder of classroom.com, author
Objectives: to really understand different memory maNagement strategies, et al
Three memory management strategies: automatic garbage collection, autorelease pool, manual allocate. And release of objects
Garbage collection not avail on ios-
RAM space ranges from 128-512 mb on ios objects, but count on much less available. There's no memory paging.
Autorelease pool is created at start of main and drained at the end of main
For cocoa and ios apps, automatically drained at end of event cycle
Multithread apps need separate pools per thread.
Framework objects are (mostly) autoreleased.
Doing example with a fraction class too much to take notes here.
Alloc involves retain - must be released.
If you release the single retained object twice (over released) error message says "released freed object"
Dealloc - never called directly, of course.
Retain count: how many people have dibs on this object?
When retain count hits zero, system invokes dealloc...
Autorelease doesn't affect retain count, but when pool is drained, the object will be released (once). The "pool" isn't a space where objects are stored - it is a list of objects that should be released when you drain the pool.
When is the pool released? Other than when you specifically tell it to? At end of event loop.
Retaining allows objects to survive after the pool is drained... From one event loop to the next.
When you add an object to an array, it sends a retain to the object. True for most methods that have "add" or "replace" in method name.
Methods with "remove" in name will release.
You can have local autorelease pool, even nested ones.
Alloc, copy*, or new must manually maintain
Autoreleased methods: static methods that return objects e.g. [nsmutabledictionary dictionary] returns an autoreleased object.
[[nsmutabledictionary alloc] init] is not autoreleased. Both have been retained once.
Trouble example: add a view to a superview and release it. Later in program, remove from superview - the view is deallocated.
Strange optimizations: constant string objects and nsnumber objects from -1 to 12 are often higher than they "should" be.
If you don't need an object in a method but are going to return it, now is a good time to autorelease.
Event cycle:
Remember that a new autorelease pool gets created when your app is to process an event. The pool gets drained when that method is done. Event is pressing a button, dragging, etc.
Example of trouble: in viewdidload method, user has said data = [nsarray array] -- it gets deleted at end of view loading event!
Could retain, could use alloc/init, or use synthesized setter method, which retains. ****But don't want to alloc AND use synthesized setter- that double retains! Causes a memory leak****
If you use @property (retain), then setter involves retaining. @property(assign) doesn't retain.
Another example: when you initWithCoder, the stuff in the coder is autoreleased, so you better do something that retains the data!
@property (copy) always makes an immutable copy, not a mutable one, even if the instance variable is of a mutable type.
When memory gets low in iPhone:
Application did receive memory warning
Release data you don't need!
Didreceivememorywarning is sent to all view controllers.
By default, views will be released if not in a superview
When view is released, viewdidunload is sent to the viewcontroller
Finding memory leaks
Put breakpoint or slog in dealloc
Use static analyzer- build and analyze puts blue icons in bak point bar. Click on blue boxes for more and more helpful info! Very neat!
Instruments - get guide from apple's website
More resources on PowerPoint that Steve posted.
- Posted using BlogPress from my iPad
Voices that matter keynote #VTM_iPhone
Here are notes from The keynote at the conference I am attending:
Aaron Hillegass keynote on independence vs interdependence
The rachael Ray of objective c.
Microwave programming (30 rock reference) - how do you get to the point where there is no more innovation? The golden age was when the cost of innovating exceeded the benefit of innovation.
Sign #1: when unit cost approaches unit price.
Sign #2: no substantial innovation in iMac since 2006 iMac, except speed... So average age of active unit approaches the half time to broken or worn out
Sign #3: trialware. Dell computer is an advertising model annoy user to become advertising source. When profits from selling something pleasing people want drops below selling things that annoy people.
Sign #4: open source tech becomes competition
Innovation free tech: microwave ovens, server os, desktop and laptop hardware, mp3 players, television
What about mobile? Mobile os?
"apple ios is significantly more mature than android."-A.H.
"who cares?"- china mobile, verizon, sprint, vodaphone, orange, t-mobile, AT&T
Mobile apps?
If we were trying to create an industry where the end of innovation came hurtling towards us?
Apps must be simple, games must be inexpensive. (games $1.22, non games $2.85),
Visiting 1998-imagine we could go back and talk to self at start of Internet. Crash left us with JavaScript, HTML looking bad in browsers, flash, silverlight. If you have an idea, now is the time to do it.
Dependence vs independence vs interdependence:
Benefits of independence: deep knowledge/control of product, flexible location and time, motivating, low burn rate, sense of ownership, lots of learning opportunities
But independence = adolescence. No synergy. References steven covey.
Specialization of labor - maybe bring more people into the fold, domain expertise, the tangible connecting to software, access to customers, camaraderie - people to talk with makes it more fun.
So get interdependent now.
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Aaron Hillegass keynote on independence vs interdependence
The rachael Ray of objective c.
Microwave programming (30 rock reference) - how do you get to the point where there is no more innovation? The golden age was when the cost of innovating exceeded the benefit of innovation.
Sign #1: when unit cost approaches unit price.
Sign #2: no substantial innovation in iMac since 2006 iMac, except speed... So average age of active unit approaches the half time to broken or worn out
Sign #3: trialware. Dell computer is an advertising model annoy user to become advertising source. When profits from selling something pleasing people want drops below selling things that annoy people.
Sign #4: open source tech becomes competition
Innovation free tech: microwave ovens, server os, desktop and laptop hardware, mp3 players, television
What about mobile? Mobile os?
"apple ios is significantly more mature than android."-A.H.
"who cares?"- china mobile, verizon, sprint, vodaphone, orange, t-mobile, AT&T
Mobile apps?
If we were trying to create an industry where the end of innovation came hurtling towards us?
Apps must be simple, games must be inexpensive. (games $1.22, non games $2.85),
Visiting 1998-imagine we could go back and talk to self at start of Internet. Crash left us with JavaScript, HTML looking bad in browsers, flash, silverlight. If you have an idea, now is the time to do it.
Dependence vs independence vs interdependence:
Benefits of independence: deep knowledge/control of product, flexible location and time, motivating, low burn rate, sense of ownership, lots of learning opportunities
But independence = adolescence. No synergy. References steven covey.
Specialization of labor - maybe bring more people into the fold, domain expertise, the tangible connecting to software, access to customers, camaraderie - people to talk with makes it more fun.
So get interdependent now.
- Posted using BlogPress from my iPad
Success!
After a week of waiting, my App was approved. If you're reading this, be sure to check out Implosion! On the app store.
- Posted using BlogPress from my iPad
- Posted using BlogPress from my iPad
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