是否可以将NULL传递给块参数？ [英] Is it okay to pass in NULL to a block parameter?

问题描述

当我将 NULL 或 nil 传入<$ c中的完成块时，iOS不会对我尖叫$ c> animateWithDuration：动画：完成：但这是否意味着没关系？或者最好打开一个空的 ^ {} ？

iOS does not scream at me when I pass in NULL or nil to the completion block in animateWithDuration:animations:completion: but does that mean it's okay? Or is it better to open an empty ^{ }?

推荐答案

这是可以的，只要您可以相信您传递 nil 的代码不会尝试将其称为块。

This is okay as long as you can trust that the code to which you are passing the nil won't try to call it as a block.

快速演示：

typedef void (^GenericBlock)(void);

void useThisBlock(GenericBlock block){
    block();
}

useThisBlock(^{NSLog(@"All okay.");});
useThisBlock(nil);    // Compiles but crashes

内部代码必须首先检查块： if （块）block（）;

The inner code must check the block first: if( block ) block();

对于UIKit代码，你应该没事。

In the case of UIKit code, you should be fine.

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