如何在Objective-C中使用NSRunLoop？

NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
[runLoop run];

// 创建一个定时器
NSTimer *timer = [NSTimer timerWithTimeInterval:1.0 target:self selector:@selector(timerFired:) userInfo:nil repeats:YES];

// 将定时器添加到NSRunLoop中
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];

- (void)timerFired:(NSTimer *)timer {
    NSLog(@"Timer fired!");
}

[runLoop performSelector:@selector(doSomething) target:self argument:nil order:0 modes:[NSArray arrayWithObject:NSDefaultRunLoopMode]];

[runLoop stop];