可可爷爷

发布于 2024-09-27 16:00:51 字数 394 浏览 4 评论 0原文

是否可以访问对象超类（或祖父）的超类方法？

例如：

GrandFatherObject : NSObject
SuperObject : GrandFatherObject
SelfObject : SuperObject

来自 SelfObject：

- (void)overriddenMethod
{
  // For Self
  someCode();

  // For Parent
  [super overriddenMethod];

  // For GrandParent
  ???
}

我只能访问 SelfObject（无法修改 SuperObject 或 GrandFatherObject）

原文

Is it possible to access the super class method of an objects super class (or grandfather)?

For instance:

GrandFatherObject : NSObject
SuperObject : GrandFatherObject
SelfObject : SuperObject

From SelfObject:

- (void)overriddenMethod
{
  // For Self
  someCode();

  // For Parent
  [super overriddenMethod];

  // For GrandParent
  ???
}

I only have access to SelfObject (Can't modify SuperObject or GrandFatherObject)

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甜宝宝 2024-10-04 16:00:51

是的，您可以做到这一点，但它需要的代码比仅仅调用 super 多一点。

或多或少，它会是这样的：

#import <objc/runtime.h>

struct objc_super grandsuper;
grandsuper.receiver = self;
grandsuper.class = class_getSuperclass(class_getSuperclass([self class]));

//if _cmd has a non-struct return value:
id grandsuperReturnValue = objc_msgSendSuper(&grandsuper, _cmd, arg1, arg2, ...);

Yes, you can do it, but it takes a bit more code than just invoking super.

More or less, it'd be something like this:

#import <objc/runtime.h>

struct objc_super grandsuper;
grandsuper.receiver = self;
grandsuper.class = class_getSuperclass(class_getSuperclass([self class]));

//if _cmd has a non-struct return value:
id grandsuperReturnValue = objc_msgSendSuper(&grandsuper, _cmd, arg1, arg2, ...);

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凉世弥音 2024-10-04 16:00:51

你为什么要这样做？如果您认为有必要，您应该重新考虑您的类设计。当然，您始终可以在父类的 overriddenMethod 实现中调用 super。

为了正确封装，子类不需要了解除父类之外的任何信息。否则，继承层次结构中就会出现紧密的双向耦合。噩梦。

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缱倦旧时光 2024-10-04 16:00:51

虽然使用 objc_msgSendSuper() 当然很有趣，但为什么不采取简单的方法并在 SelfObject 实现中创建一个类别，就像

@interface SuperObject (ForSelfObject)
  - (id)grandFatherOverridenMethod;
@end

@implementation SuperObject (ForSelfObject)
  - (id)grandFatherOverridenMethod {
    return [super overridenMethod];
  }
@end

你说你不能修改 SuperObject，这并不意味着你不能扩展它。我在这里遗漏了任何主要缺点吗？

While playing with objc_msgSendSuper() is certainly fun, why don't you take the easy way and create a Category in the SelfObject implementation, something like

@interface SuperObject (ForSelfObject)
  - (id)grandFatherOverridenMethod;
@end

@implementation SuperObject (ForSelfObject)
  - (id)grandFatherOverridenMethod {
    return [super overridenMethod];
  }
@end

You said you can't modify SuperObject, that doesn't mean you can't extend it. Am I missing any major drawbacks here?

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