Objective-C是否允许循环依赖? [英] Does Objective-C allow circular dependencies?

问题描述

我正在用Objective-C重写Java库，但遇到了一种奇怪的情况.我有两个互相导入的类.这是一个循环依赖性. Objective-C是否支持这种情况?如果没有，您如何建议我重写它?

I'm rewriting a Java library in Objective-C and I've come across a strange situation. I've got two classes that import each other. It's a circular dependency. Does Objective-C support such a situation? If not, how do you recommend I rewrite it?

推荐答案

导入类不是继承. Objective-C不允许循环继承，但允许循环依赖.您要做的是使用@class指令在彼此的标头中声明这些类，并让每个类的实现文件导入另一个人的标头.发挥作用:

Importing a class is not inheritance. Objective-C doesn't allow circular inheritance, but it does allow circular dependencies. What you would do is declare the classes in each other's headers with the @class directive, and have each class's implementation file import the other one's header. To wit:

@class ClassB;

@interface ClassA : NSObject {
    ClassB *foo;
}
@end

ClassA.m

#import "ClassB.h"

@implementation ClassA
    // Whatever goes here
@end

ClassB.h

@class ClassA;

@interface ClassB : NSObject {
    ClassA *foo;
}

@end

ClassB.m

#import "ClassA.h"

@implementation ClassB
    // Whatever goes here
@end

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