包括头文件与实现文件（C ++） [英] including files in header vs implementation file (C++)

问题描述

您好，我只有一个简短的问题。

这

例如：

  // test.h 
 #includeglobals.h
 
 class Test 
 {
 Test（）; 
}; 
  

vs

  // test.cpp 
 #includeglobals.h
 
 Test :: Test（）
 {
} 
  




解决方案

一般原则是你希望尽可能减少依赖， / p>



• 如果您的接口（.h）引用了给定标题中的任何内容， ＃include in the interface（.h）




• 如果您只引用不在您的界面中），那么您应该只在实现中包含该标头

所以对于上面的例子，如果你不引用任何东西从globals.h在test.h，但你引用它在test.cpp，然后#include应该在test.cpp。如果你在test.h中引用globals.h中的任何内容，那么你需要在test.h中加入#include。

Hi I just have a quick question. What's the difference between including a header file in a header file vs including it in a implementation file?

This

Ex:

// test.h
#include"globals.h"

class Test
{
    Test();
};

vs

//test.cpp
#include"globals.h"

Test::Test()
{
}

解决方案

The general principle is that you want to minimise dependencies wherever reasonably possible, so:

• if your interface (.h) references anything in a given header then that header needs to be #included in the interface (.h)

• if you only reference a given header in your implementation (.cpp) (and not in your interface) then you should only #include that header in the implementation

• you should also try to only #include headers that are actually needed, although this can be difficult to maintain during the lifetime a large project

So for your example above, if you don't reference anything from globals.h in test.h, but you do reference it in test.cpp, then the #include should go in test.cpp. If you reference anything from globals.h in test.h though then you need the #include in test.h.

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