C++中的operator的兩種用法
阿新 • • 發佈：2019-02-06
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std ;
/*
C++中的operator主要有兩個作用，
第一種: 操作符的過載，一是自定義物件型別的隱式轉換。
第二種: 自定義物件型別的隱式轉換 使用格式 operator 型別()
*/
class A
{
public:
A( int a )
{
this->a = a;
}
~A() {}
//-------------運算子過載-------------
A & operator = (const A &a)
{
cout << "過載=運算子" << endl;
this->a = a.a;
return *this ;
}
A operator + ( const A &a)
{
cout << "過載+運算子" << endl;
return A(this->a + a.a);
}
string operator()()
{
cout << "過載()運算子" << endl;
return string("aaa");
}
int operator()(int b)
{
cout << "過載()運算子 帶引數" << endl;
return b;
}
int operator<<(int b)
{
cout << "過載()運算子 帶引數" << endl;
return b;
}
bool operator == (const A&a)
{
cout << "過載==運算子" << endl;
return (this->a == a.a);
}
A* operator & ()
{
cout << "過載&運算子" << endl;
return this;
}
char operator [] (int i)
{
cout << "過載[]運算子" << endl;
return i+'a' ;
}
A * operator -> ()
{
cout << "過載->運算子" << endl;
return this;
}
ostream & operator << (ostream& o )
{
cout << "過載<<運算子" << endl;
o << a << endl;
return o;
}
istream & operator >> (istream& i)
{
cout << "過載>>運算子" << endl;
cin>> a;
return i;
}
//-------------型別轉換-------------
operator float()
{
cout << "強制轉換為float" << endl;
return a*0.1f;
}
operator const char()
{
cout << "強制轉換為 const char" << endl;
return 'f';
}
operator string()
{
cout << "強制轉換為string" << endl;
return string("hehe");
}
int a;
};
int main() {
A a(11);
A a1(0);
a1 = a;
cout << a1.a << endl;
A a2(22);
A a3 = a1 + a2;
cout << a3.a << endl;
string a4= a1();
cout << a4 << endl;
int a5 = a2(333);
cout << a5 << endl;
cout <<( a1==a2)<< endl;
A *a6 = &a1;
cout << a6->a << endl;
char a7 = a2[4];
cout << a7 << endl;
cout << a1->a<<endl;
a2 >> cin;//採用友元函式更好
a2 << cout;//採用友元函式更好
//-------------------自動隱式轉換--------------------------
float t1 = a1;
cout << t1 << endl;
const char t2 = (const char) a1;
cout << t2 << endl;
string t3 = a1;
cout << t3 << endl;
}
#include <iostream>
#include <string>
using namespace std ;
/*
C++中的operator主要有兩個作用，
第一種: 操作符的過載，一是自定義物件型別的隱式轉換。
第二種: 自定義物件型別的隱式轉換 使用格式 operator 型別()
*/
class A
{
public:
A( int a )
{
this->a = a;
}
~A() {}
//-------------運算子過載-------------
A & operator = (const A &a)
{
cout << "過載=運算子" << endl;
this->a = a.a;
return *this ;
}
A operator + ( const A &a)
{
cout << "過載+運算子" << endl;
return A(this->a + a.a);
}
string operator()()
{
cout << "過載()運算子" << endl;
return string("aaa");
}
int operator()(int b)
{
cout << "過載()運算子 帶引數" << endl;
return b;
}
int operator<<(int b)
{
cout << "過載()運算子 帶引數" << endl;
return b;
}
bool operator == (const A&a)
{
cout << "過載==運算子" << endl;
return (this->a == a.a);
}
A* operator & ()
{
cout << "過載&運算子" << endl;
return this;
}
char operator [] (int i)
{
cout << "過載[]運算子" << endl;
return i+'a' ;
}
A * operator -> ()
{
cout << "過載->運算子" << endl;
return this;
}
ostream & operator << (ostream& o )
{
cout << "過載<<運算子" << endl;
o << a << endl;
return o;
}
istream & operator >> (istream& i)
{
cout << "過載>>運算子" << endl;
cin>> a;
return i;
}
//-------------型別轉換-------------
operator float()
{
cout << "強制轉換為float" << endl;
return a*0.1f;
}
operator const char()
{
cout << "強制轉換為 const char" << endl;
return 'f';
}
operator string()
{
cout << "強制轉換為string" << endl;
return string("hehe");
}
int a;
};
int main() {
A a(11);
A a1(0);
a1 = a;
cout << a1.a << endl;
A a2(22);
A a3 = a1 + a2;
cout << a3.a << endl;
string a4= a1();
cout << a4 << endl;
int a5 = a2(333);
cout << a5 << endl;
cout <<( a1==a2)<< endl;
A *a6 = &a1;
cout << a6->a << endl;
char a7 = a2[4];
cout << a7 << endl;
cout << a1->a<<endl;
a2 >> cin;//採用友元函式更好
a2 << cout;//採用友元函式更好
//-------------------自動隱式轉換--------------------------
float t1 = a1;
cout << t1 << endl;
const char t2 = (const char) a1;
cout << t2 << endl;
string t3 = a1;
cout << t3 << endl;
}