How to realize it?

[weixj2003ld]

I have created class A in a.h and a.cpp,and class B in b.h and b.cpp;

One method of A needs B,like this,

class A
{
    ...
      void method_A1(B b);
    ...
}

class A
{
    ...
      void method_A1(B b);
    ...
}

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So the file b.h needs to be included in a.h.

now one method of B needs A,like this,

class B
{
    ...
      void method_B1(A b);
    ...
}

class B
{
    ...
      void method_B1(A b);
    ...
}

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So the file a.h needs to be included in b.h.

the program runs normally,but I think the two header files are included each other,it is odd.

Could you tell me how to deal with it normally?