Download as KEY, PPTX
![Example
- (void)blink:(UIColor *)color
{
self.view.backgroundColor = color;
[UIView animateWithDuration:1.0
animations:^{self.view.backgroundColor = [UIColor
darkGrayColor];}];
}
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-26-2048.jpg)
![Thread init
newThread = [[NSThread alloc] initWithTarget:self
selector:@selector(newThreadEntryPoint:) object:nil];
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-39-2048.jpg)
![Thread start
[newThread start];
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-41-2048.jpg)
![Housekeeping
- (void)newThreadEntryPoint:(id)param
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]
init];
…
}
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-42-2048.jpg)
![Event sources
NSInputStream *catnipStream;
[catnipStream setDelegate:self];
[catnipStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
forMode:NSDefaultRunLoopMode];
[catnipStream open];
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-44-2048.jpg)
![Running the loop
do {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
beforeDate:[NSDate distantFuture]];
} while (!done);
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-45-2048.jpg)
![The whole package
- (void)runThread
{
newThread = [[NSThread alloc] initWithTarget:self selector:@selector(newThreadEntryPoint:)
object:nil];
[newThread start];
}
- (void)newThreadEntryPoint:(id)param
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[catnipStream setDelegate:self];
[catnipStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[catnipStream open];
do {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
} while (!done);
}
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-46-2048.jpg)
![Run loop maintenance
do {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
beforeDate:[NSDate distantFuture]];
} while (!done);
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-48-2048.jpg)
![Run loop maintenance
do {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
beforeDate:[NSDate distantFuture]];
} while ([[NSThread currentThread] isCancelled] == NO);
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-49-2048.jpg)
![Run loop maintenance
do {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
beforeDate:[NSDate dateWithTimeIntervalSinceNow:5]];
} while ([[NSThread currentThread] isCancelled] == NO);
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-50-2048.jpg)
![Clean up!
[catnipStream close];
[catnipStream removeFromRunLoop:[NSRunLoop currentRunLoop]
forMode:NSDefaultRunLoopMode];
[catnipStream setDelegate:nil];
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-51-2048.jpg)
![A lot of code?
- (void)runThread
{
newThread = [[NSThread alloc] initWithTarget:self selector:@selector(newThreadEntryPoint:)
object:nil];
[newThread start];
}
- (void)newThreadEntryPoint:(id)param
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[catnipStream setDelegate:self];
[catnipStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[catnipStream open];
do {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate
dateWithTimeIntervalSinceNow:5]];
} while ([[NSThread currentThread] isCancelled] == NO);
[catnipStream close];
[catnipStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[catnipStream setDelegate:nil];
[pool drain];
}
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-52-2048.jpg)
![More maintenance
Consider draining the autorelease pool from within
the loop if the thread will be running for a long time
do {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate
dateWithTimeIntervalSinceNow:5]];
[pool drain];
pool = [[NSAutoreleasePool alloc] init];
} while ([[NSThread currentThread] isCancelled] == NO);
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-53-2048.jpg)
![How to quit?
[newThread cancel];
Safe to use from any thread
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-54-2048.jpg)
![Solution
performSelectorOnMainThread:(SEL)aSelector
withObject:(id)arg waitUntilDone:(BOOL)wait
(on secondary thread)
[self
performSelectorOnMainThread:@selector(updateField
s:) withObject:data waitUntilDone:YES];
© 2011](https://image.slidesharecdn.com/cracow-mobi-120102095232-phpapp01/75/Threading-in-iOS-Cocoa-Touch-58-2048.jpg)
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Threading in iOS / Cocoa Touch
- 1.
- 2. About Me Used tobe a Linux kernel developer Currently developing hardware accessories for iOS © 2011
- 3. What this talkisn’t about © 2011
- 4. What this talkisn’t about Hardware accessories © 2011
- 5. What this talkisn’t about Hardware accessories App Store overnight success © 2011
- 6. What this talkisn’t about Hardware accessories App Store overnight success POSIX threads © 2011
- 7. 150% thread content © 2011
- 8. Plan 1. Why welove and hate threads 2. Grand Central Dispatch 3. NSThread class © 2011
- 9. Threading ©2011
- 10. Threading Not only formulti-core chips © 2011
- 11. Threading Not only formulti-core chips Responsiveness is the king © 2011
- 12. Threading Not only formulti-core chips Responsiveness is the king “The snappy” © 2011
- 13. Threading Not only formulti-core chips Responsiveness is the king “The snappy” Asynchronicity © 2011
- 14.
- 15. General solution Threads © 2011
- 16. Downsides Overhead Especially on embeddedsystems #1 issue: threads are difficult © 2011
- 17. Really? Thread management IPC, messaging,synchronization Locking Reentrancy ??? © 2011
- 18.
- 19. Grand Central Dispatch Languagefeatures Runtime libraries System enhancements © 2011
- 20.
- 22. Language features: blocks Small,self-contained pieces of code Anonymous, inline collection of code Available: Snow Leopard, iOS 4.0 © 2011
- 23. Blocks features Typed arguments Returnvalue Access (and modify) variables © 2011
- 24. Mainly useful as Callbacks Self-containedunits of work © 2011
- 25. Syntax BOOL (^block)(void); BOOL areKittensCute= YES; block = ^{ return areKittensCute; }; © 2011
- 26. Example - (void)blink:(UIColor *)color { self.view.backgroundColor = color; [UIView animateWithDuration:1.0 animations:^{self.view.backgroundColor = [UIColor darkGrayColor];}]; } © 2011
- 28. Grand Central API GCDprovides FIFO queues for blocks Three types: Main Concurrent Serial © 2011
- 29. Concurrent queues Blocks dequeuedin FIFO order … but run concurrently if resources allow Finish in any order Created automatically © 2011
- 30. Serial queues Useful forserialization of tasks Created manually dispatch_queue_create(“com.yourname.queue”, NULL); © 2011
- 31. Really? Thread management IPC, messaging,synchronization Locking Reentrancy ??? © 2011
- 32. When queues arenot enough Dispatch sources © 2011
- 33. Dispatch source API C-levelAPI Can monitor for events (signals, data) and dispatch handlers to appropriate queues Low-level, useful for OS X but maybe not for iOS © 2011
- 34. Back to squareone NSThread class © 2011
- 35. The real thing Costof threads: Creation time Memory footprint (512 kB) Design overhead © 2011
- 36. Conclusion — Don’t use threads! © 2011
- 37. … unless you haveno other choice High level event monitoring © 2011
- 38. Thread lifecycle 1. Initialize 2.Start 1. Create autorelease pool, setup sources 2. Do work 3. Cancel 4. Drain pool © 2011
- 39. Thread init newThread =[[NSThread alloc] initWithTarget:self selector:@selector(newThreadEntryPoint:) object:nil]; © 2011
- 40.
- 41.
- 42. Housekeeping - (void)newThreadEntryPoint:(id)param { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; … } © 2011
- 43. Get to work Twooptions: Execute a predefined workset Monitor for events Run loop © 2011
- 44. Event sources NSInputStream *catnipStream; [catnipStreamsetDelegate:self]; [catnipStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [catnipStream open]; © 2011
- 45. Running the loop do{ [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]; } while (!done); © 2011
- 46. The whole package -(void)runThread { newThread = [[NSThread alloc] initWithTarget:self selector:@selector(newThreadEntryPoint:) object:nil]; [newThread start]; } - (void)newThreadEntryPoint:(id)param { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; [catnipStream setDelegate:self]; [catnipStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [catnipStream open]; do { [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]; } while (!done); } © 2011
- 47. Reuse & recycle Whatif I need on-demand threads? © 2011
- 48. Run loop maintenance do{ [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]; } while (!done); © 2011
- 49. Run loop maintenance do{ [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]; } while ([[NSThread currentThread] isCancelled] == NO); © 2011
- 50. Run loop maintenance do{ [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:5]]; } while ([[NSThread currentThread] isCancelled] == NO); © 2011
- 51. Clean up! [catnipStream close]; [catnipStreamremoveFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [catnipStream setDelegate:nil]; © 2011
- 52. A lot ofcode? - (void)runThread { newThread = [[NSThread alloc] initWithTarget:self selector:@selector(newThreadEntryPoint:) object:nil]; [newThread start]; } - (void)newThreadEntryPoint:(id)param { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; [catnipStream setDelegate:self]; [catnipStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [catnipStream open]; do { [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:5]]; } while ([[NSThread currentThread] isCancelled] == NO); [catnipStream close]; [catnipStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; [catnipStream setDelegate:nil]; [pool drain]; } © 2011
- 53. More maintenance Consider draining the autorelease pool from within the loop if the thread will be running for a long time do { [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:5]]; [pool drain]; pool = [[NSAutoreleasePool alloc] init]; } while ([[NSThread currentThread] isCancelled] == NO); © 2011
- 54. How to quit? [newThreadcancel]; Safe to use from any thread © 2011
- 55. Conclusions iOS applications areheavily threaded internally Main thread, web rendering thread etc. GCD is also implemented via threads © 2011
- 56. Caveats Key-value observers arealways executed in the current thread context What happens when KVO from secondary threads is used to handle or update UI outlets? © 2011
- 58. Solution performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait (on secondarythread) [self performSelectorOnMainThread:@selector(updateField s:) withObject:data waitUntilDone:YES]; © 2011
- 59. Why? Responsiveness! © 2011
- 60. Questions? Karol Kozimor karol.kozimor@iosyn.com © 2011
- 61. More info Concurrency ProgrammingGuide Operation Queues Threading Programming Guide WWDC 2011: Blocks and Grand Central Dispatch in Practice © 2011
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