Objective-C，定期在后台运行NSTask

Question

我看到了一些关于如何在后台运行NSTask的好信息，尽管这并不完全是我想做的。我想做是定期在后台运行一个NSTask（比如每30秒），然后杀死它；下面可能是我想做的一个例子：

NSTask *theTask = [ [ NSTask alloc ] init ];
NSPipe *taskPipe = [ [ NSPipe alloc ] init ];
[ theTask setStandardError:taskPipe ];
[ theTask setStandardOutput:taskPipe ];
[ theTask setLaunchPath:@"/bin/ls" ];
[ theTask setArguments:[ NSArray arrayWithObject:@"-l" ] ];
[ theTask launch ];
// Wait 30 seconds, then repeat the task

Answer 1

也许你可以简单地让线程进入睡眠状态，并在do循环中等待30秒：

do {
[ theTask launch ]; //Launch the Task
sleep(30);          //Sleep/wait 30 seconds 
} while (someCondition);

否则，您可以使用NSTimer:

NSTimer *t = [NSTimer scheduledTimerWithTimeInterval: 30.0
                      target: self
                      selector:@selector(onTick:)
                      userInfo: nil repeats:YES];

- (void)onTick:(NSTimer *)timer {
    //In this method that will be get called each 30 seconds, 
    //you have to put the action that you want to perform ...
    [ theTask launch ];
}