使用類成員函數訪問類內的私有結構

Question

嘗試爲類內的私有結構編寫setter函數。還沒有找到允許訪問結構的聲明方法。

該結構可能不能移出課程。該函數必須是該類的成員。前向聲明可能不被使用。

class Editor 
{ 
public: 
    void setName (string s); 
private: 
    struct Object 
    { 
     string name; 
    }Instance; 
}Ed; 

void Editor::setName (string s) 
{ 
    name = s; // no access 
} 

==================================

class Editor 
{ 
public: 
    friend void setName (Editor &m , string s); 
private: 
    struct Object 
    { 
     int name; 
    }Instance; 
}Ed; 

void setName (Editor &m , string s) 
{ 
    name = s; // no access 
} 

== ================================

class Editor 
{ 
public: 
    friend void setName (Object &m , string s); //invalid declaration ( Object is undefined) 
private: 
    struct Object 
    { 
     string name; 
    }Instance; 
}Ed; 

Answer 1

void Editor::setName (string s) 
{ 
    name = s; // no access 
} 

當然，你不能做那種事。 Editor中沒有名爲name的對象。但是，有一個名爲Instance的對象包含對象名爲name，您可以使用Instance.name = s;設置該值。

Answer 2

什麼：

class Editor 
{ 
public: 
    void setName (string s); 
private: 
    struct Object 
    { 
     string name; 
    }Instance; 
}Ed; 

void Editor::setName (string s) 
{ 
    Instance.name = s; 
}