两个类和内联函数 [英] Two classes and inline functions

问题描述

我有两个类，并且两个类都使用其他类，例如：

  // class1.h 
 class Class1; 
 #includeclass2.h
 
 class Class1 {
 public：
 static Class2 * C2; 
 ... 
}; 
 
 // class2.h 
 class Class2; 
 #includeclass1.h
 
 class Class2 {
 public：
 static Class1 * C1; 
 ... 
}; 
  

当我像上面的例子中定义它，它工作（我也有一些 #ifndef 以避免无限头recurency）。但我也想添加一些内联函数到我的类。我阅读了这里，我应该把内联函数的定义放在头文件，因为它不会工作，如果我将它们放在cpp文件，并希望从其他cpp文件调用（当我这样做，我得到未定义的引用链接期间）。但这里的问题是这样的：

  // class1.h 
 ... 
 inline void Class1 :: Foo（）{
 C2-> Bar（）; 
} 
  

我得到错误：无效使用不完整的类'struct Class2' p>

那么我该如何做呢？

解决方案

头文件，然后包括它，并定义你的内联方法。通过在每个标题中执行此操作，它们是自给自足的，并且包括一个将始终包括另一个，其中包含包含警卫防止无限递归。

A.hpp

  #ifndef INCLUDE_GUARD_B9392DB18D114C1B8DFFF9B6052DBDBD 
 #define INCLUDE_GUARD_B9392DB18D114C1B8DFFF9B6052DBDBD 
 
 struct B; 
 
 struct A {
 B * p; 
 void foo（）; 
}; 
 
 #includeB.hpp
 
 inline 
 void A :: foo（）{
 if（p）p-> bar ）; 
} 
 
 #endif 
  

B.hpp

  #ifndef INCLUDE_GUARD_C81A5FEA876A4C6B953D1EB7A88A27C8 
 #define INCLUDE_GUARD_C81A5FEA876A4C6B953D1EB7A88A27C8 
 
 struct A; 
 
 struct B {
 A * p; 
 void bar（）; 
}; 
 
 #includeA.hpp
 
 inline 
 void B :: bar（）{
 if（p）p-> foo ）; 
} 
 
 #endif 
  

I have two classes and both of them uses some of the other class, on example:

// class1.h
class Class1;
#include "class2.h"

class Class1 {
  public:
  static Class2 *C2;
  ...
};

// class2.h
class Class2;
#include "class1.h"

class Class2 {
  public:
  static Class1 *C1;
  ...
};

And when I define it like in example above, it works (I also have some #ifndef to avoid infinite header recurency). But I also want to add some inline functions to my classes. And I read here that I should put definition of inline function in header file, because it won't work if I'll put them in cpp file and want to call them from other cpp file (when I do it I get undefined reference during linking). But the problem here is with something like this:

// class1.h
...
inline void Class1::Foo() {
  C2->Bar();
}

I get error: invalid use of incomplete type ‘struct Class2’.

So how can I do it?

解决方案

You need to delay including the header, but then include it and define your inline methods. By doing this in each header, they are self-sufficient and including one will always include the other, with include guards preventing infinite recursion.

A.hpp

#ifndef INCLUDE_GUARD_B9392DB18D114C1B8DFFF9B6052DBDBD
#define INCLUDE_GUARD_B9392DB18D114C1B8DFFF9B6052DBDBD

struct B;

struct A {
  B* p;
  void foo();
};

#include "B.hpp"

inline
void A::foo() {
  if (p) p->bar();
}

#endif

B.hpp

#ifndef INCLUDE_GUARD_C81A5FEA876A4C6B953D1EB7A88A27C8
#define INCLUDE_GUARD_C81A5FEA876A4C6B953D1EB7A88A27C8

struct A;

struct B {
  A* p;
  void bar();
};

#include "A.hpp"

inline
void B::bar() {
  if (p) p->foo();
}

#endif

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