[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(searchDataNetWork) object:nil];
[self performSelector:@selector(searchDataNetWork) withObject:nil afterDelay:0.5];
searchDataNetWork 就是网络请求的方法
[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(searchDataNetWork) object:nil];
[self performSelector:@selector(searchDataNetWork) withObject:nil afterDelay:0.5];
searchDataNetWork 就是网络请求的方法