scheduleInRunLoop作用
例子一：
- - (void)setUpStreamForFile:(NSString *)path {
- // iStream is NSInputStream instance variable
- iStream = [[NSInputStream alloc] initWithFileAtPath:path];
- [iStream setDelegate:self];
- [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
- forMode:NSDefaultRunLoopMode];
- [iStream open];
- }
上面的例子显示，当你创建对象之后你应该设置其delegate。当把NSInputStream对象配置到一个run loop，并且有与流相关的事件(例如流中有可读数据)发生时，该对象会收到stream:handleEvent:消息。
在你open stream之前，给流对象发送一个scheduleInRunLoop:forMode: 消息，来将该对象配置到一个run loop接收stream events。这样，当流中没有数据可读时可以避免delegate阻塞。如果流是发生在另一个线程，你需要确认该流对象是配置在那个线程的run loop中。你不应该尝试从一个除了包含该流对象的run loop的线程的其他线程中对流进行操作。最后，对NSInputStream对象发送open消息开始对输入数据的流操作。
例子二：
- 1 NSURLRequest *request = ...
- 2 NSURLConnection *connection = [[NSURLConnection alloc]
- initWithRequest:request
- delegate:self
- startImmediately:NO];
- 3 [connection scheduleInRunLoop:[NSRunLoop currentRunLoop]
- forMode:NSRunLoopCommonModes];
- 4 [connection start];
- 第3句的作用：
The reason the connection delegate messages aren't firing until you stop scrolling is because during scrolling, the run loop is in UITrackingRunLoopMode. By default, NSURLConnection schedules itself in NSDefaultRunLoopMode only, so you don't get any messages while scrolling.
