cancelPreviousPerformRequestsWithTarget

本文详细介绍了如何在代码中执行和取消执行特定操作的方法,包括使用`performSelector:withObject:afterDelay:`和`cancelPreviousPerformRequestsWithTarget:selector:object:`函数。这些方法对于实现定时任务和操作控制至关重要。

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1.执行

[self performSelector:@selector(showNextMessage) withObject:nil afterDelay:1];

2.取消

[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(showNextMessage) object:nil];

Cancels perform requests previously registered with performSelector:withObject:afterDelay:.


All perform requests are canceled that have the same target as aTarget, argument as anArgument, and selector as aSelector. This method removes perform requests only in the current run loop, not all run loops.






- (void)close { // Empty queues. [self emptyQueues]; [partialReadBuffer release]; partialReadBuffer = nil; [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(disconnect) object:nil]; // Close streams. if (theReadStream != NULL) { CFReadStreamSetClient(theReadStream, kCFStreamEventNone, NULL, NULL); CFReadStreamUnscheduleFromRunLoop (theReadStream, theRunLoop, kCFRunLoopDefaultMode); CFReadStreamClose (theReadStream); CFRelease (theReadStream); theReadStream = NULL; } if (theWriteStream != NULL) { CFWriteStreamSetClient(theWriteStream, kCFStreamEventNone, NULL, NULL); CFWriteStreamUnscheduleFromRunLoop (theWriteStream, theRunLoop, kCFRunLoopDefaultMode); CFWriteStreamClose (theWriteStream); CFRelease (theWriteStream); theWriteStream = NULL; } // Close sockets. if (theSocket != NULL) { CFSocketInvalidate (theSocket); CFRelease (theSocket); theSocket = NULL; } if (theSocket6 != NULL) { CFSocketInvalidate (theSocket6); CFRelease (theSocket6); theSocket6 = NULL; } if (theSource != NULL) { CFRunLoopRemoveSource (theRunLoop, theSource, kCFRunLoopDefaultMode); CFRelease (theSource); theSource = NULL; } if (theSource6 != NULL) { CFRunLoopRemoveSource (theRunLoop, theSource6, kCFRunLoopDefaultMode); CFRelease (theSource6); theSource6 = NULL; } theRunLoop = NULL; // If the client has passed the connect/accept method, then the connection has at least begun. // Notify delegate that it is now ending. if (theFlags & kDidPassConnectMethod) { // Delay notification to give him freedom to release without returning here and core-dumping. if ([theDelegate respondsToSelector: @selector(onSocketDidDisconnect:)]) { //[theDelegate performSelector:@selector(onSocketDidDisconnect:) withObject:self afterDelay:0]; [theDelegate onSocketDidDisconnect:self]; } } // Clear flags. theFlags = 0x00; }
06-13
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