如果環路運行asynchoursly

Question

大家好，我想創建循環是否與此代碼asynchoursly運行：

NSString *care = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:@"http://localhost/untitled.txt"]]; 
if (care == @"ONRED") { //untitled.txt = ONRED 
    [red_on setHidden:NO]; 
    [red_off setHidden:YES]; 
} 

我怎麼可以運行if語句就像一個循環？

Answer 1

如果我得到你的權利，你可以把這些語句的方法，並呼籲performSelectorInBackground：

(void)asyncMethod { 
    NSString *care = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:@"http://localhost/untitled.txt"]]; 
    if (care == @"ONRED") { //untitled.txt = ONRED 
     [red_on setHidden:NO]; 
     [red_off setHidden:YES]; 
    } 
} 

// in some other method 
[self performSelectorInBackground:@selector(asyncMethod) withObject:nil]; 

另一種選擇是使用大中央調度（如this answer描述）：

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 
             (unsigned long)NULL), ^(void) { 
    NSString *care = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:@"http://localhost/untitled.txt"]]; 
     if (care == @"ONRED") { //untitled.txt = ONRED 
      [red_on setHidden:NO]; 
      [red_off setHidden:YES]; 
     } 
});