在C ++中应该声明哪些类？ [英] In which order should classes be declared in C++?

问题描述

说我有这个C ++代码：

Say I got this C++ code:

class class1{
    class2 *x;
}

class class2{
    class1 *x;
}

编译器会在第2行给出错误，因为它无法找到class2 ，和相同，如果我切换类的顺序。如何解决这个问题？

The compiler would give an error in line 2 because it couldn't find class2, and the same if i switched the order of the classes. How do I solve this?

推荐答案

有两件事 - 一类，在类声明后需要分号：

Two things - one, you need semicolons after class declarations:

class class1{
    class2 *x;
};

class class2{
    class1 *x;
};

二，可以在类的定义之前创建一个声明。这告诉编译器这个类存在，你还没有定义它。在这种情况下，在 class1 的定义前放置 class2 声明：

Two, you can create a declaration in front of the definitions of the classes. That tells the compiler that this class exists, and you have yet to define it. In this case, put a class2 declaration in front of the definition of class1:

class class2 ;

class class1{
    class2 *x;
};

class class2{
    class1 *x;
};

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