目标 C 中的朋友类 [英] Friend class in Objective C

问题描述

我正在将 cpp 代码移植到 Objective C.

I am porting cpp code into Objective C.

在cpp中，我们可以将一个类作为friend class添加到另一个类中，并使用其所有公共函数和变量.

In cpp we can add a class as friend class to another class and use all its public functions and variables.

我知道Objective C 不支持友元类 概念.

我如何在Objective C中将一个类作为另一个类的朋友

How do i make a class as a friend to another class in Objective C

推荐答案

如果您有两个紧耦合的类，那么您可以使用一些简单的技巧来公开一个更简单的公共接口.例如，

If you have two tightly-coupled classes, then you can use some simple tricks to expose a simpler public interface. For example,

在 Banana.h 中:

@interface Banana : NSObject
- (BOOL)isPeeled;
@end

在 Monkey.h 中:

@interface Monkey : NSObject
- (void)eat:(Banana *)aBanana;
@end

在 BananaPrivate.h 中:

@interface Banana (PrivateMethods)
- (void)peel;
@end

然后你的 Monkey.m 文件可以导入 BananaPrivate.h 来获取私有函数.如果您正在编写框架，则不要在框架标头中包含 BananaPrivate.h.

Then your Monkey.m file can import BananaPrivate.h to get the private functions. If you're writing a framework, then you don't include BananaPrivate.h in your framework headers.

这与在 C 中完成封装的方式相同.在我看来，它比 C++ 中的 friend 关键字破坏性要小得多，但这超出了本答案的范围解释原因.

This is the same way encapsulation is done in C. In my opinion it's significantly less broken than the friend keyword in C++, but it's beyond the scope of this answer to explain why.

如果您将 Banana 实现为类集群，您也可以通过这种方式公开私有成员变量，但这有点疯狂，我不推荐这样做.如果您需要类之间更紧密的耦合，您可能希望在该部分代码中使用 C 习语.

You can also expose private member variables this way if you implement Banana as a class cluster, but that's kind of insane and I don't recommend it. If you need even closer coupling between classes you might want to use C idioms for that part of the code.

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