c++學習 --- 類和物件之運算子過載
阿新 • • 發佈：2021-08-16
五、運算子過載
1、加號運算子過載
#include <iostream> #include <string> using namespace std; //加號運算子過載 class Person { public: //1.成員函式過載+號 Person operator+(Person &p) { Person temp; temp.m_A = this->m_A + p.m_A; temp.m_B = this->m_B + p.m_B; return temp; }int m_A; int m_B; }; //2.全域性函式過載+號 //Person operator+(Person &p1, Person &p2) { // Person temp; // temp.m_A = p1.m_A + p2.m_A; // temp.m_B = p1.m_B + p2.m_B; // return temp; //} //運算子過載也可以發生函式過載 Person operator+(Person &p1, int num) { Person temp; temp.m_A = p1.m_A + num; temp.m_B= p1.m_B + num; return temp; } void test01() { Person p1; p1.m_A = 10; p1.m_B = 10; Person p2; p2.m_A = 10; p2.m_B = 10; //成員函式過載本質呼叫 //Person p3 = p1.operator+(p2); //全域性函式過載本質呼叫 //Person p3 = operator+(p1, p2); //簡寫成 Person p3 = p1 + p2; //運算子過載也可以發生函式過載Person p4 = p1 + 100; cout << "p3.m_A = " << p3.m_A << endl; cout << "p3.m_B = " << p3.m_B << endl; cout << "p4.m_A = " << p4.m_A << endl; cout << "p4.m_B = " << p4.m_B << endl; } int main() { test01(); system("pause"); return 0; }
2、左移運算子過載
#include <iostream> #include <string> using namespace std; //左移運算子過載 class Person { //過載左移運算子配合友元可以實現輸出自定義資料型別 friend ostream & operator<<(ostream &out, Person &p); public: Person(int a, int b) :m_A(a),m_B(b){ } //1.利用成員函式過載左移運算子 //不會利用成員函式過載<<運算子，因為無法實現cout在左側 /* void operator<<(Person &p) ==> p.operator<<(p) 不合適 void operator<<(cout) ==> p.operator<<(cout) 簡化版本 p << cout ，cout不在左側，不合適 */ private: int m_A; int m_B; }; //2.利用 全域性函式實現左移運算子 /*本質 operator<<(cout,&p) 簡化 cout << p ostream 輸出流物件只能有一個，用引用的方式引數傳遞 返回ostream 鏈式程式設計思想可以用於追加輸出別的內容 */ ostream & operator<<(ostream &out,Person &p) { //友元支援訪問類中私有成員變數 out << "m_A = " << p.m_A << " m_B = " << p.m_B; return out; } void test01() { //建構函式賦初值 Person p(10,10); //鏈式程式設計 //<< 返回ostream的物件 可以後面輸出<< " Hello world" << endl; cout << p << " Hello world" << endl; } int main() { test01(); system("pause"); return 0; }
3、遞增運算子過載
#include <iostream> #include <string> using namespace std; //過載遞增運算子 //自定義整形 class MyInterger { friend ostream& operator<<(ostream& cout, MyInterger myint); public: MyInterger():m_Num(0){} //過載前置++運算子 //為什麼返回引用，不返回值 /* 和真實前置++一致 ++(++a) 2 a 2 而返回值： ++(++myint) 2 myint 1 前後兩次不是一個物件，第一次加後對新的物件做了遞增 */ MyInterger& operator++() { m_Num++; //先++ return *this; //再將自身做返回 } //過載後置++運算子 /* void operator++(int) 其中int代表佔位引數 可以用於區分前置和後置（只認int） 為什麼返回值，不返回引用 返回區域性物件，當前函式執行完後釋放，物件被釋放 返回引用，後續是非法操作 */ MyInterger operator++(int) { MyInterger temp = *this; //先記錄當時的結果 m_Num++; //後遞增 return temp; //最後將記錄結果返回 } private: int m_Num; }; //全域性函式 << 運算子過載 ostream& operator<<(ostream& cout, MyInterger myint) { cout << myint.m_Num; return cout; } void test01() { MyInterger myint; cout << ++(++myint) << endl; //2 cout << myint << endl; //2 } void test02() { MyInterger myint; cout << myint++ << endl; //0 cout << myint << endl; //1 } int main() { test01(); //test02(); system("pause"); return 0; }
#include <iostream> #include <string> using namespace std; //過載遞減運算子 class MyInterger { friend ostream& operator<<(ostream & cout, MyInterger mint); public: MyInterger() :m_Num(10) {} //前置-- MyInterger& operator--() { --m_Num; return *this; } //後置-- MyInterger operator--(int) { MyInterger temp = *this; m_Num--; return temp; } private: int m_Num; }; ostream& operator<<(ostream & cout, MyInterger mint) { cout << mint.m_Num; return cout; } void test01() { MyInterger myint; cout << --(--myint) << endl; //8 cout << myint << endl; //8 } void test02() { MyInterger myint; cout << myint-- << endl; //10 cout << myint << endl; //9 } int main() { test01(); test02(); system("pause"); return 0; }
4、賦值運算子過載
#include <iostream> #include <string> using namespace std; //賦值運算子過載 class Person { public: Person(int age) { m_Age = new int(age); //堆區 } ~Person() { if (m_Age != NULL) { delete m_Age; //手動釋放 m_Age = NULL; } } //過載賦值運算子 Person& operator=(Person &p) { //編譯器提供的時淺拷貝 //m_Age = p.m_Age; //應該先判斷是否有屬性在堆區，如果有，先釋放乾淨，然後再深拷貝 if (m_Age != NULL) { delete m_Age; m_Age = NULL; } //深拷貝 m_Age = new int(*p.m_Age); return *this; } int * m_Age; }; void test01() { Person p1(18); Person p2(20); Person p3(30); p1 = p2 = p3; //賦值操作，預設淺拷貝，在解構函式釋放時暴露問題 cout << "p1的年齡: " << *p1.m_Age << endl; cout << "p2的年齡: " << *p2.m_Age << endl; cout << "p3的年齡: " << *p3.m_Age << endl; } int main() { test01(); system("pause"); return 0; }
5、關係運算符過載
#include <iostream> #include <string> using namespace std; //關係運算符過載 class Person { public: Person(string name, int age) { m_Name = name; m_Age = age; } //過載 == 號 bool operator==(Person &p) { if (this->m_Name == p.m_Name && this->m_Age == p.m_Age) { return true; } else return false; } //過載 != 號 bool operator!=(Person &p) { if (this->m_Name == p.m_Name && this->m_Age == p.m_Age) { return false; } else { return true; } } string m_Name; int m_Age; }; void test01() { Person p1("Tom", 18); Person p2("Tom", 18); if (p1 == p2) { cout << "p1和p2是相等的" << endl; } else { cout << "p1和p2是不相等的" << endl; } if (!(p1 != p2)) { cout << "p1和p2是相等的" << endl; } else { cout << "p1和p2是不相等的" << endl; } } int main() { test01(); system("pause"); return 0; }
6、函式呼叫運算子過載
#include <iostream> #include <string> using namespace std; //函式呼叫運算子過載 //列印類 class Myprint { public: void operator()(string text) { cout << text << endl; } }; //加法類 class Myadd { public: int operator()(int num1,int num2) { return num1 + num2; } }; void MyPrint02(string text) { cout << text << endl; } void test01() { Myprint myFunc; //仿函式，使用起來非常類似於函式呼叫 myFunc("hello world"); //物件使用過載的小括號 MyPrint02("hello world"); //函式呼叫 } //仿函式非常靈活，沒有固定的寫法 void test02() { Myadd myadd; int ret = myadd(100,100); cout << "ret = " << ret << endl; //匿名函式物件,Myadd();(100,100) 過載的函式呼叫運算子 cout << Myadd()(100, 200) << endl; } int main() { test01(); test02(); system("pause"); return 0; }