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

构造函数

析构函数

运算符重载

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;
}