接下来会分析平时使用中常接触到的 RACImmediateScheduler、RACQueueScheduler 和 RACSubscriptionScheduler 3个子类
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+ (RACScheduler *)currentScheduler {
RACScheduler *scheduler = NSThread.currentThread.threadDictionary[RACSchedulerCurrentSchedulerKey];
if (scheduler != nil) return scheduler;
if ([self.class isOnMainThread]) return RACScheduler.mainThreadScheduler;
return nil;
}
+ (BOOL)isOnMainThread {
return [NSOperationQueue.currentQueue isEqual:NSOperationQueue.mainQueue] || [NSThread isMainThread];
}
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+ (RACScheduler *)immediateScheduler {
static dispatch_once_t onceToken;
static RACScheduler *immediateScheduler;
dispatch_once(&onceToken, ^{
immediateScheduler = [[RACImmediateScheduler alloc] init];
});
return immediateScheduler;
}
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+ (RACScheduler *)mainThreadScheduler {
static dispatch_once_t onceToken;
static RACScheduler *mainThreadScheduler;
dispatch_once(&onceToken, ^{
mainThreadScheduler = [[RACTargetQueueScheduler alloc] initWithName:@"org.reactivecocoa.ReactiveObjC.RACScheduler.mainThreadScheduler" targetQueue:dispatch_get_main_queue()];
});
return mainThreadScheduler;
}
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+ (RACScheduler *)subscriptionScheduler {
static dispatch_once_t onceToken;
static RACScheduler *subscriptionScheduler;
dispatch_once(&onceToken, ^{
subscriptionScheduler = [[RACSubscriptionScheduler alloc] init];
});
return subscriptionScheduler;
}
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- (void)scheduleRecursiveBlock:(RACSchedulerRecursiveBlock)recursiveBlock addingToDisposable:(RACCompoundDisposable *)disposable {
@autoreleasepool {
RACCompoundDisposable *selfDisposable = [RACCompoundDisposable compoundDisposable];
[disposable addDisposable:selfDisposable];
__weak RACDisposable *weakSelfDisposable = selfDisposable;
RACDisposable *schedulingDisposable = [self schedule:^{
@autoreleasepool {
[disposable removeDisposable:weakSelfDisposable];
}
if (disposable.disposed) return;
void (^reallyReschedule)(void) = ^{
if (disposable.disposed) return;
[self scheduleRecursiveBlock:recursiveBlock addingToDisposable:disposable];
};
__block NSLock *lock = [[NSLock alloc] init];
lock.name = [NSString stringWithFormat:@"%@ %s", self, sel_getName(_cmd)];
__block NSUInteger rescheduleCount = 0;
__block BOOL rescheduleImmediately = NO;
@autoreleasepool {
recursiveBlock(^{
[lock lock];
BOOL immediate = rescheduleImmediately;
if (!immediate) ++rescheduleCount;
[lock unlock];
if (immediate) reallyReschedule();
});
}
[lock lock];
NSUInteger synchronousCount = rescheduleCount;
rescheduleImmediately = YES;
[lock unlock];
for (NSUInteger i = 0; i < synchronousCount; i++) {
reallyReschedule();
}
}];
[selfDisposable addDisposable:schedulingDisposable];
}
}
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- (RACDisposable *)schedule:(void (^)(void))block {
NSCParameterAssert(block != NULL);
RACDisposable *disposable = [[RACDisposable alloc] init];
dispatch_async(self.queue, ^{
if (disposable.disposed) return;
[self performAsCurrentScheduler:block];
});
return disposable;
}
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