c++ 操作符重載

c++ 操作符重載

 

 

 /* file = main.cpp 涉及操作符重載，友元函數，重載類型轉換*/
#include <iostream>
#include "testClass.h"
using namespace std;

int main()
{
    testClass tc1(2);
    testClass tc2(3);
    testClass tc3 = 1 + tc1 + tc2 + 4;// 重載加法
    testClass tc4 = 5 - tc2 - tc1 - 1;// 重載減法
    int a = tc1;// 重載了類型轉換
    cout << "tc3:= " << tc3 << ", tc4:=" << tc4 << endl;
    // 重載了類型轉換才能用下面這樣的語句
    cout << "tc3 + t4 := " << tc3 + tc4 << endl;
    cout << "tc3 - t4 := " << tc3 - tc4 << endl;
    return 0;
}
/* file = testClass.h */
#ifndef TESTCLASS_H
#define TESTCLASS_H
#include <iostream>
class testClass
{
    public:
        testClass(int i);
        virtual ~testClass();
        testClass operator +(testClass & sf) const;
        testClass operator +(int j) const;
        testClass operator -(testClass & sf) const;
        testClass operator -(int j) const;
        operator int() const;// 重載類型轉換；必須是成員函數，零參數，無傳回值
        friend testClass operator +(int j, testClass & sf);
        friend testClass operator -(int j, testClass & sf);
        friend std::ostream & operator <<(std::ostream & os, testClass & sf);
    protected:
    private:
        int m_i;
};

#endif // TESTCLASS_H

/* file = testClass.cpp */
#include "testClass.h"

testClass::testClass(int i)
{
    this->m_i = i;
}

testClass::~testClass()
{
}

testClass testClass::operator +(testClass & sf) const{
testClass tc(this->m_i + sf.m_i);
return tc;
}

testClass testClass::operator +(int j) const{
testClass tc(this->m_i + j);
return tc;
}

testClass operator +(int j, testClass & sf){
   return sf + j;
}

testClass testClass::operator -(testClass & sf) const{
testClass tc(this->m_i - sf.m_i);
return tc;
}

testClass testClass::operator -(int j) const{
testClass tc(this->m_i - j);
return tc;
}

testClass operator -(int j, testClass & sf){
testClass tc(j - sf.m_i);
return tc;
}

testClass::operator int() const{
return this->m_i;
}

std::ostream & operator <<(std::ostream & os, testClass & sf){
    os << sf.m_i;
    return os;
}
共含三個檔案，在winxp + codeblock 8.02 上測試通過，由於codeblock 新建立的類檔案標頭檔放在include路徑下，需要在project -> build options -> Search directories -> Compiler -> Add , 添加一個include 路徑，否則codeblock 會報告找不到標頭檔"testClass.h"