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要進行operator overloading , 一般來說有兩種形式 , 分別是non-member function 以及 nonstatic member function .
non-member function一般來說較為容易理解 , 但是若要讓他能夠存取class內的private data , 則要將他宣告為friend function.
But ..writing friend functions that modify private member variables of a class is generally not considered good coding style, as it violates encapsulation.
Follow is the example of these two methods.
non-member function :
class Cents{private: int m_nCents;public: Cents(int nCents) { m_nCents = nCents; } // Overload cCents + int friend Cents operator+(Cents &cCents, int nCents); int GetCents() { return m_nCents; }};// note: this function is not a member function!Cents operator+(Cents &cCents, int nCents){ return Cents(cCents.m_nCents + nCents);}
nonstatic member functionclass Cents{private: int m_nCents;public: Cents(int nCents) { m_nCents = nCents; } // Overload cCents + int Cents operator+(int nCents); // 可以想成是把int當做argument傳入給cCents int GetCents() { return m_nCents; }};// note: this function is a member function!Cents Cents::operator+(int nCents){ return Cents(m_nCents + nCents);}
ref : http://www.learncpp.com/cpp-tutorial/96-overloading-operators-using-member-functions/
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