可以创建“块”的类别，对象在Objective-C [英] Is it possible to create a category of the "Block" object in Objective-C

问题描述

我想为Objective-C块创建一个类别来添加函数。

I would like to add functions by creating a category for Objective-C Blocks.

__block int (^aBlock)(int) = ^int( int n ){
    if( n <= 1 ) return n;
    return aBlock( n - 1 ) + aBlock( n - 2 );
};

而不是只允许正常的 [aBlock copy] ， [aBlock retain] ， [aBlock release] ， / code>。我可以做类似的事情：

Instead of just allowing the normal [aBlock copy], [aBlock retain], [aBlock release], [aBlock autorelease]. I could do thing like:

[aBlock mapTo:anArray];

可能的类别

@interface UnknownBlockClass (map)

- (NSArray *)mapTo:(NSArray *)array_;

@end

推荐答案

pwc是正确的，因为你不能为你看不到的类创建类别。

@pwc is correct in that you can't create a category for a class that you can't see.

但是...

1. 一些运行时内省揭示了一些有趣的信息。有许多类包含单词Block。其中一些看起来很有前景： __ NSStackBlock ， __ NSMallocBlock ， __ NSAutoBlock 和 NSBlock 。


2. 一些更自省显示有希望的类继承自 NSBlock

1. Some runtime introspection reveals some interesting information. There are a number of classes that contain the word "Block". Some of them look promising: __NSStackBlock, __NSMallocBlock, __NSAutoBlock, and NSBlock.
2. Some more introspection shows that the promising classes inherit from NSBlock

所以看起来任何块都会是 NSBlock 。

So it looks like any block is going to be some instance or subclass of NSBlock.

您可以在对象上创建方法，如下所示：

You can create a method on an object, like so:

@implementation Foo
- (void) doFoo {
  //do something awesome with self, a block
  //however, you can't do "self()".  
  //You'll have to cast it to a block-type variable and use that
}
@end

然后在运行时，可以将该方法移动到 NSBlock 类：

Then at runtime, you can move that method to the NSBlock class:

Method m = class_getInstanceMethod([Foo class], @selector(doFoo));
IMP doFoo = method_getImplementation(m);
const char *type = method_getTypeEncoding(m);
Class nsblock = NSClassFromString(@"NSBlock");
class_addMethod(nsblock, @selector(doFoo), doFoo, type);

之后，块应该响应 doFoo 消息。

After this, blocks should respond to the doFoo message.

这篇关于可以创建“块”的类别，对象在Objective-C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！