使用NSTimer传递原始参数的正确方法 [英] Proper way of passing a primitive argument with an NSTimer

问题描述

我使用一个基本的计时器来调用这个方法：

   - （void）refresh：（id）obj 
 {
 if（obj == YES）doSomething; 
} 
  

我想从我的代码的某些区域调用此方法，计时器

  [NSTimer scheduledTimerWithTimeInterval：refreshInterval 
 target：self 
 selector：@selector b $ b userInfo：nil 
 repeats：YES]; 
  

当我把 YES userInfo 参数，我得到一个 EXC_BAD_ACCESS 错误;为什么是这样？

有人可以帮我做这个正确的方式，这样没有丑陋的投射等等？

它是键入 id 。 YES 是一个原始值，即值 1 。为了确保 userInfo 对象不会被释放，定时器保留它。所以，当你通过 YES ，NSTimer做 [（id）YES retain] 。尝试在你自己的代码，看看会发生什么。 :-P

如文档说明，您给出的选择器必须具有签名

   - （void）timerFireMethod：（NSTimer *）theTimer 
  pre> 
 
 
这意味着你不能有NSTimer调用任何方法 - 至少不直接。 
 
 
 
所以，假设你有一个名为 refresh的方法，你可以使用上面的签名来创建一个特殊的方法， ：，并且你想经常调用它，传递 YES 。您可以这样做：
  // somehere 
 {
 [NSTimer scheduledTimerWithTimeInterval：refreshInterval 
 target：self 
 selector：@selector（invokeRefresh :) 
 userInfo：nil 
 repeats：YES]; 
} 
 
  - （void）invokeRefresh：（NSTimer *）timer {
 [self refresh：YES]; 
} 
 
  - （void）refresh：（BOOL）flag {
 if（flag）{
 // do something 
} 
 } 
  
 
I'm using a basic timer that calls this method:
- (void) refresh:(id)obj
{
    if (obj == YES) doSomething;
}
I want to call this method from certain areas of my code and also from a timer
[NSTimer scheduledTimerWithTimeInterval:refreshInterval
                            target:self
                            selector:@selector(refresh:) 
                            userInfo:nil 
                            repeats:YES];
When I put YES as the argument for the userInfo parameter, I get an EXC_BAD_ACCESS error; why is this?

Can someone help me do this the right way so that there is no ugly casting and such?
解决方案
The userInfo parameter must be an object; it is typed id. YES is a primitive, namely the value 1. In order to make sure the userInfo object does not get deallocated, the timer retains it. So, when you passed YES, NSTimer was doing [(id)YES retain]. Try that in your own code and see what happens. :-P

As the Documentation states, the selector you give the method must have the signature
- (void)timerFireMethod:(NSTimer*)theTimer
This means you can't have an NSTimer invoke just any method—not directly at least. You can make a special method with the above signature which in turn invokes any method you want though.

So, say you have a method called refresh:, and you want to call it every so often, passing it YES. You can do this like so:
// somewhere
{
    [NSTimer scheduledTimerWithTimeInterval:refreshInterval
                                     target:self
                                   selector:@selector(invokeRefresh:)
                                   userInfo:nil
                                    repeats:YES];
}

- (void)invokeRefresh:(NSTimer *)timer {
    [self refresh:YES];
}

- (void)refresh:(BOOL)flag {
    if (flag) {
        // do something
    }
}


                        
这篇关于使用NSTimer传递原始参数的正确方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！