Effective Objective-C 2.0メモ

gistfile1.m

// 読み出しを通常のブロック, 書き込みをバリアブロックとして並列キューで処理
_syncQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

- (NSString *)someString
{
    __block NSString *localSomeString;
    dispatch__sync(_syncQueue, ^{
        localSomeString = _someString;
    });
    return localSomeString;
}

- (void)setSomeString:(NSString *)someString
{
    dispatch_barrier_async(_syncQueue, ^{
        _someString = someString;
    });
}


// コンパイル時に代入できないstatic定数はinitializeをオーバーライドして初めてクラスが使われるタイミングで設定
static const int kInterval = 10;
static NSMutableArray *kSomeObjects;

@implementation EOCClass

+ (void)initialize
{
    if (self == [EOCClass class]) {
        kSomeObjects = [NSMutableArray new];
    }
}

@end


// NSTimerの循環参照を防ぐためにブロックを受け取るAPIをカテゴリで定義
@interface NSTimer (EOCBlocksSupport)

+ (void)eoc_scheduledTimerWithTimeInterval:(NSTimeInterval)interval
                                     block:(void(^)())block
                                   repeats:(BOOL)repeats;

@end

@implementation NSTimer (EOCBlocksSupport)

+ (void)eoc_scheduledTimerWithTimeInterval:(NSTimeInterval)interval
                                     block:(void(^)())block
                                   repeats:(BOOL)repeats
{
    return [self scheduledTimerWithTimeInterval:interval
                                         target:self
                                       selector:@selector(eoc_blockInvoke:)
                                       userInfo:[block copy]
                                        repeats:repeats];
}

+ (void)eoc_blockInvoke:(NSTimer*)timer
{
    void (^block)() = timer.userInfo;
    if (block) {
        block();
    }
}

@end

// selfは弱参照に代入してからブロックの中で使う
- (void)startPolling
{
    __weak EOCClass *weakSelf = self;
    _pollTimer =
    [NSTimer eoc_scheduledTimerWithTimeInterval:5.0
                                          block:^{
        __strong EOCClass *strongSelf = weakSelf;
        [strongSelf p_doPoll];
    }
                                        repeats:YES];
}