面向对象程序设计-C++ Default constructor & Copy constructor& Destructor & Operator Overloading【第九次上课笔记】

先上笔记内容吧：

这次上课的内容有关

1. 构造函数
2. 析构函数
3. 运算符重载
4. return * this

　　内容很细，大家好好回顾笔记再照应程序复习吧　:)

#include <iostream>

using namespace std;

class Integer {
public:
    int i;
    int geti () const {return this->i;}
    void seti (int i) {this->i = i;}
    Integer(int j = 0);
    Integer(Integer & c);
    ~Integer();
};

Integer::Integer (Integer & c) {    //Constructer Function
    i = 18;
    cout << "Integer (Integer & c)" << endl;
}

Integer::Integer (int j) : i(j) {   //Copy Constructer Function
    cout << "Integer (int j)" << endl;
}

Integer::~Integer () {              //Destructer Function
    cout << "~Integer () " << endl;
}

const Integer & fun (const Integer & in) {
    cout << in.geti () << endl;
    return in;
}

int main (){

    Integer b(8);
    fun(b).geti();
    Integer a(b);

    return 0;
}

下面这个程序是有关运算符重载

通过　log print 可以跟踪观察到析构的顺序

同时还有引用返回、友元函数的例子

#include <iostream>

using namespace std;

class Integer {
private:
    int i;
public:
    int geti () const {return this->i;}
    void seti (int i) {this->i = i;}
    Integer(int j = 0);
    Integer(Integer & c);
    ~Integer();

    const Integer & operator = (const Integer & in);
    friend const Integer operator + (const Integer & lhs, const Integer & rhs);
};

const Integer & Integer::operator = (const Integer & in) {  //Member Function
    i = in.i + 50;
    //return in;
    return *this;
}

const Integer operator + (const Integer & lhs, const Integer & rhs) { //全局函数
    Integer out;
    out.i = lhs.i + rhs.i;
    return out;
}

Integer::Integer (Integer & c) {    //Constructer Function
    i = 18;
    cout << "Integer (Integer & c)" << endl;
}

Integer::Integer (int j) : i(j) {   //Copy Constructer Function
    cout << "Integer (int j)" << ' ' << j << endl;
}

Integer::~Integer () {              //Destructer Function
    cout << "~Integer () " << ' ' << i << endl;
}

int main (){

    Integer b(8), a, c, d;
    cout << "a.geti()" << a.geti() << endl;
    d = c = a = b;
    cout << "a.geti()" << a.geti() << endl;
    cout << "c.geti()" << c.geti() << endl;
    cout << "d.geti()" << d.geti() << endl;

    d = a + b;
    cout << "d.geti()" << d.geti() << endl;

    return 0;
}

 接下来运算符重载作一些附加说明

• =
• &
• ,

这三个运算符可以直接使用

运算符重载的时候，如果既有 成员函数，又有全局函数， 优先(?)　　

eg.

++i (前加) Integer & operator ++ ()
i++ (后加) Integer & operator ++ (int)
括号中的 int 仅仅表示后加，无其他含义

下面的这个例子可以帮助大家更好的理解

#include <iostream>

using namespace std;

class Integer {
private:
    int i;
public:
    int geti () const {return this->i;}
    void seti (int i) {this->i = i;}
    Integer(int j = 0);
    Integer(Integer & c);
    ~Integer();

    Integer & operator ++ ();
    Integer operator ++ (int);
    const Integer & operator = (const Integer & in);
    friend const Integer operator + (const Integer & lhs, const Integer & rhs);
};

Integer & Integer::operator ++ () {
	++i;
	return *this;
}

Integer Integer::operator ++ (int) {
	Integer temp (this->i);
	++temp.i;
	return temp;
}

const Integer & Integer::operator = (const Integer & in) {  //Member Function
    i = in.i;
    //return in;
    return *this;
}

const Integer operator + (const Integer & lhs, const Integer & rhs) { //全局函数
    Integer out;
    out.i = lhs.i + rhs.i;
    return out;
}

Integer::Integer (Integer & c) {    //Constructer Function
    i = 18;
    cout << "Integer (Integer & c)" << endl;
}

Integer::Integer (int j) : i(j) {   //Copy Constructer Function
    cout << "Integer (int j)" << ' ' << j << endl;
}

Integer::~Integer () {              //Destructer Function
    cout << "~Integer () " << ' ' << i << endl;
}

int main (){

	Integer b(8), a;
	cout << b.geti () << "," << a.geti () << endl;
	a = ++b;
	cout << b.geti () << "," << a.geti () << endl;
    a = b++;
    cout << b.geti () << "," << a.geti () << endl;

    return 0;
}