如何从类方法中使用委派（或传递消息） [英] How to use delegation (or pass messages) from class methods

问题描述

我有一个类视图控制器调用的类方法。我希望视图控制器知道什么时候类方法完成了任务（它有线程）。

我想我应该使用委托，但我需要一个 id委托，我不能通过 self.delegate 调用它，因为类方法中没有自己。

我该怎么做？

谢谢！

解决方案

您可以在类级别（甚至与对象级委托分开）中存储代理，但对我来说听起来有点腥。你可以这样做：

在你的头文件中：

  @interface SomeClass：SomeBaseClass 
 {
 ... 
} 
 
 ... 
 +（id< SomeDelegateProtocol>）classDelegate 
 +（void）setClassDelegate（id< SomeDelegateProtocol>）委托
 +（void）myCleanupClassMethod 
 
 @end 
  

在您的实现文件中：

  @implementation SomeClass 
 ... 
 
 static id< SomeDelegateProtocol> _classDelegate = nil; 
 
 +（id< SomeDelegateProtocol>）classDelegate 
 {
 return _classDelegate; 
} 
 
 +（void）setClassDelegate（id< SomeDelegateProtocol> delegate 
 {
 _classDelegate = delegate; 
} 
 
 +（void）myCleanupClassMethod 
 {
 if（[_classDelegate responsesToSelector：@selector（theDelegateMethod :)]）
 {
 [_classDelegate theDelegateMethod：something]; 
} 
} 
 
 @end 
  

为了真正使用这段代码，你只需像类对象级别的委托一样设置类级别的代理，并等待它被调用（您需要确定何时调用 myCleanupClassMethod ）：

  //项目中的其他地方
 [SomeClass setClassDelegate：self]; 
  

I have a class method that gets called by a view controller. I want the view controller to be aware of when the class method has finished its tasks (it has threads on it).
I think I should use delegation, but I need an id delegate, and I can't call it by self.delegate, because there is no self in a class method.

How should I do this?
Thanks!

解决方案

You can store a delegate at class-level (even separate from an object-level delegate), but it sounds a bit fishy to me. Here's how you'd do it:

In your header file:

@interface SomeClass : SomeBaseClass
{
...
}

...
+ (id<SomeDelegateProtocol>)classDelegate
+ (void)setClassDelegate(id<SomeDelegateProtocol>) delegate
+ (void)myCleanupClassMethod

@end

In your implementation file:

@implementation SomeClass
...

static id<SomeDelegateProtocol> _classDelegate = nil;

+ (id<SomeDelegateProtocol>)classDelegate
{
    return _classDelegate;
}

+ (void)setClassDelegate(id<SomeDelegateProtocol> delegate
{
    _classDelegate = delegate;
}

+ (void)myCleanupClassMethod
{
    if ([_classDelegate respondsToSelector:@selector(theDelegateMethod:)])
    {
        [_classDelegate theDelegateMethod:something];
    }
}

@end

To actually use this code, you simply set the class-level delegate like an object-level delegate and wait for it to be called (you need to decide when myCleanupClassMethod is invoked):

// Somewhere else in the project
[SomeClass setClassDelegate:self];

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