ios - 在搜索栏中的时间间隔后执行函数 - Objective-C

Question

我想如果用户在搜索栏中输入文本后保持空闲 3 秒则执行一个函数。我尝试使用以下代码:

- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText {    
  ...    
    if ([searchText length] >= 3) { // If text length is greater than 3

      [NSRunLoop cancelPreviousPerformRequestsWithTarget:self 
               selector:@selector(searchBarSearchButtonClicked:) object:searchBar];

      [self performSelector:@selector(searchBarSearchButtonClicked:)
                               withObject:searchBar afterDelay:3.0]; 

   }

}

此代码的问题是，如果用户输入大于 3 的文本并按回车键，然后代码执行两次，有时它会因“无效计时器”而崩溃。。 p>

上面的代码应该做哪些修改？

Answer 1

我通过使用 NSTimer 找到了解决方案。以下是片段:

- (void) searchBar:(UISearchBar *)theSearchBar textDidChange:(NSString *)searchText {

    [timer invalidate];
    timer = nil;    
    ...

    if ([searchText length] >= 3) { 

       timer = [NSTimer scheduledTimerWithTimeInterval: 3.0 target: self
             selector: @selector(SearchBarProxyCall) userInfo:nil repeats: NO];   
    }
}

- (void)searchBarSearchButtonClicked:(UISearchBar *)searchBar {
    [timer invalidate];
    timer = nil;

    ...
}

-(void)SearchBarProxyCall { 
    [self searchBarSearchButtonClicked:searchbar];
}