A simple question of a C++ function

Here is a class

Code:

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class Complex{
private:
int real, image;
public:
Complex(int r=0, int i=0):real(r),image(i){}

int GetReal() {return real;}
int GetImage() {return image;}

void foo(const Complex & rhs){
cout<<rhs.GetImage()<<endl;
return;
}
};

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When I compile it, it reports:

Quote:

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In foo method: error C2662: 'Complex::GetImage' : cannot convert 'this' pointer from 'const Complex' to 'Complex &'

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What does it mean?

Since rhs is a const object, you can only call its members which are marked const, so try this:

Code:

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int GetReal() const {return real;}
int GetImage() const {return image;}

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Thank you. I revised the function as:

Code:

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void foo(const Complex & rhs){
cout<<rhs.image<<endl;
return;
}

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It works, but my question is that 'image' is private of 'rhs', how can you visit a private variable of rhs outside (rhs.image)?

Quote:

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Originally Posted by JaWiB

Since rhs is a const object, you can only call its members which are marked const, so try this:

Code:

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int GetReal() const {return real;}
int GetImage() const {return image;}

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JaWiB proposed a good solution to your problem, but you implemented another.

The reason your change compiles is because classes are friends with themselves, and thus can access private members. I don't think I've ever seen a tutorial mention this, but adding "friend class Complex" to your class will yield this error in gcc:

Code:

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someclass.cpp:6: error: class `Complex' is implicitly friends with itself

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