c++学习笔记

1.构造函数举例

#include 
using namespace std;
class cube {
public:
	double vol() { return x * y * z; };
	cube(double a, double b, double c);
private:
	double x, y, z;
};
cube::cube(double a, double b, double c) {
	x = a;
	y = b;                       //利用构造函数来初始化对象中数据成员的值
	z = c;
}
int main()
{
	cube a(1, 2, 5);
	cube b(5, 63, 3.2);
	cout << a.vol() << endl;
	cout << b.vol() << endl;
	return 0;
}

2.构造函数初始化列表举例

#include 
using namespace std;
class cube {
public:
	double vol() { return x * y * z; };
	cube(double a, double b, double c);
private:
	double x, y, z;
};
cube::cube(double a, double b, double c) :x(a),y(b),z(c)  //初始化列表
{
}
int main()
{
	cube a(1, 2, 5);
	cube b(5, 63, 3.2);
	cout << a.vol() << endl;
	cout << b.vol() << endl;
	return 0;
}

3.构造函数重载举例 两个叫point的构造函数 不同的方法来初始化。

#include 
using namespace std;
class point {
public:
	void print() { cout << x << endl; cout << y << endl; }
	point(int i, int j) :x(i), y(j) {}
	point() { x = y = 0; }
private:
	int x,y;
};
int main()
{
	point a;
	point b(1, 2);
	a.print();
	b.print();
	return 0;
}

4.带默认参数的构造函数

#include 
using namespace std;
class point {
public:
	void print() { cout << x << " "; cout << y << endl; }
	point(int i=0, int j=0) :x(i), y(j) {}
private:
	int x,y;
};
int main()
{
	point a;
	point b(1, 2);
	point c(1);
	point d(2);
	a.print();
	b.print();
	c.print();
	d.print();
	return 0;
}

5.深复制与浅复制举例

#include 
#include 
using namespace std;
class ca {
public:
	ca(int b, char* cstr)
	{
		a = b;
		str = new char[b];
		strcpy(str, cstr);
	}
	ca(const ca& c)
	{
		a = c.a;
		str = new char[a];
		if (str != 0)strcpy(str, c.str);
	}
	void show() { cout << str << endl; }
	~ca() { delete str; }
private:
	int a;
	char* str;
};
int main()
{
	ca a(10, "sdsds");
	ca b = a;
	b.show(); 
	return 0;
}

6.this指针举例

7.赋值兼容规则举例

此程序花里胡哨，因为照抄的老师。

关键点在于看work函数的形参的三种不同形式，代表了赋值兼容规则的三种情况，派生类对象赋值给1基类对象，派生类赋值给基类的2引用和3指针

#include 
using namespace std;
class man
{
protected:
	int age;
	string name;
public:
	man(int a,string n):age(a),name(n){}
	void print() { cout << "姓名：" << name << "，年龄：" << age << endl; }
	int get_age() { return age; }
	string get_name() { return name; }
};
class superman :public man
{
private:
	int force_value;
public:
	superman(int a,string n,int f):man(a,n),force_value(f){}
	void print() { cout << "姓名是" << name << "年龄是" << age << "武力值为" << force_value << endl; }
	void fly() { cout << "fly fly 82002222" << endl; }
};
int work(man a)
{
	if (a.get_age() >= 20)return 1;
	return 0;
}
int main()
{
	int n;
	man i(25, "武则天");
	superman j(22, "ssssss", 200);
	n = work(j);
	if (n != 0)cout << j.get_name() << "牛逼" << endl;
	else cout << j.get_name() << "垃圾" << endl;
	return 0;
}

int work(man *a)
{
	if (a->get_age() >= 20)return 1;
	return 0;
}
int main()
{
	int n;
	man i(25, "武则天");
	superman j(22, "ssssss", 200);
	n = work(&j);
	if (n != 0)cout << j.get_name() << "牛逼" << endl;
	else cout << j.get_name() << "垃圾" << endl;
	return 0;
}

int work(man &a)
{
	if (a.get_age() >= 20)return 1;
	return 0;
}
int main()
{
	int n;
	man i(25, "武则天");
	superman j(22, "ssssss", 200);
	n = work(j);
	if (n != 0)cout << j.get_name() << "牛逼" << endl;
	else cout << j.get_name() << "垃圾" << endl;
	return 0;
}

35.1析构函数举例
构造函数和析构函数调用顺序相反。

#include 
using namespace std;
class A {
public:
	A() { cout << "A constructor" << endl; }
	~A() { cout << "A destructor" << endl; }
};
class B :public A {
public:
	B() { cout << "B constructor" << endl; }
	~B() { cout << "B destructor" << endl; }
};
class C :public B {
public:
	C() { cout << "C constructor" << endl; }
	~C() { cout << "C destructor" << endl; }
};
int main()
{
	C t1;
	return 0;
}

35.2析构函数和构造函数举例2
没啥可说的，很简单的输入输出程序，读一下就行。

就是学生的一个类，里边有学生信息

#include 
#include
using namespace std;
class Undergraduate {
protected:
	int num;
	string name;
	char sex;
public:
	Undergraduate(int n, string nam, char se) {
		num = n; name = nam; sex = se;
	}
	~Undergraduate(){}
}; 
class garduate_stu :public Undergraduate {
private:
	int age;
	string addr;
public:
	garduate_stu(int n, string nam, char se, int ag, string add) :Undergraduate(n, nam, se) {
		age = ag; addr = add;
	}
	void show() {
		cout << "num = " << num << " name =" << name
			<< "sex= " << sex << "age= " << age << " address=" << addr << endl;
	}
	~garduate_stu(){}
};
int main()
{
	garduate_stu stu1(0021, "li yang", '1', 23, " hebeis");
	garduate_stu stu2(0022, "liu li", '1', 20, " hesssssssbeis");
	stu1.show();
	stu2.show();
	return 0;
}

36.1多重继承举例

#include 
#include
using namespace std;
class base1 {
private:
	int b1;
public:
	base1() { b1 = 0; cout << "默认构造函数base1: b1 = " << b1 << endl; }
	base1(int i):b1(i){ cout << "构造函数base1: b1 = " << b1 << endl; }
};
class base2 {
private:
	int b2;
public:
	base2() { b2 = 0; cout << "默认构造函数base2: b2 = " << b2 << endl; }
	base2(int j) :b2(j) { cout << "构造函数base2: b2 = " << b2 << endl; }
};
class base3 {
public:
	base3() { cout << "默认构造函数base3" << endl; }
};
class Derive :public base1, public base2, public base3 {
private:
	base1 memberbase1;
	base2 memberbase2;
	base3 memberbase3;
public:
	Derive() { cout <<"默认构造函数Derive "<< endl; }
	Derive(int a,int b,int c,int d):base1(a),base2(b),memberbase1(c),memberbase2(d){
		cout<<"构造Derive" << endl;
	}
};
int main()
{
	cout<<"创建派生类Derive对象obj1" << endl;
	Derive obj1;
	cout << "创建派生类Derive对象obj2" << endl;
	Derive obj2(1,2,3,4);
	return 0;
}

程序运行结果如下：关注调用顺序以及调用的构造函数还是默认构造函数。

创建派生类Derive对象obj1
默认构造函数base1: b1 = 0
默认构造函数base2: b2 = 0
默认构造函数base3
默认构造函数base1: b1 = 0
默认构造函数base2: b2 = 0
默认构造函数base3
默认构造函数Derive
创建派生类Derive对象obj2
构造函数base1: b1 = 1
构造函数base2: b2 = 2
默认构造函数base3
构造函数base1: b1 = 3
构造函数base2: b2 = 4
默认构造函数base3
构造Derive

36.2虚基类举例

重点关注A的fun函数，被B1和B2继承，而C又继承了B1和B2，因此相当于C有两个fun函数，因此需要在A类的所有直接派生类中声明virtual。这样就不会产生二义性了。

#include 
#include
using namespace std;
class A {
public:
	A(int n) :nv(n) { cout << "调用A的构造函数" << endl; }
	void fun() { cout<<"fun of A" << endl; }
private:
	int nv;
};
class B1:virtual public A{
public:
	B1(int a) :A(a) { cout<<"派生类B1的构造函数" << endl; }
private:
	int nv1;
};
class B2 :virtual public A {
public:
	B2(int a) :A(a) { cout << "派生类B2的构造函数" << endl; }
private:
	int nv2;
};
class C :public B1, public B2 {
public:
	C(int a) :A(a), B1(a), B2(a) { cout<<"C类的构造函数"<< endl; }
	void fund() { cout<<"fun of C" << endl; }
private:
	int nvd;
};
int main()
{
	C c1(1);
	c1.fund();
	c1.fun();
	return 0;
}

运行结果：
调用A的构造函数
派生类B1的构造函数
派生类B2的构造函数
C类的构造函数
fun of C
fun of A

36.4多重继承应用举例

#include 
#include
using namespace std;
enum Color {Red,Yellow,Green,White};
class Circle {
private:
	float radius;
public:
	Circle(float r) :radius(r) { cout<<"circle initialized" << endl; }
	~Circle() { cout<<"circle destroyed" << endl; }
	float Area() { return 3.1415926 * radius * radius; }
};
class Table {
	float height;
public:
	Table(float h) :height(h) { cout<<"Table initialized "<< endl; }
	~Table() { cout << "Table destroyed" << endl; }
	float Height() { return height; }
}; 
class RoundTable :public Table, public Circle {
	Color color;
public:
	RoundTable(float h, float r, Color c) :Table(h), Circle(r), color(c) {
		cout << "RoundTable initialized ! " << endl;
	}
	int GetColor() { return color; }
	~RoundTable() { cout << "RoundTable destroyed" << endl; }
};
int main()
{
	RoundTable cir_table(2.3, 5.3, Yellow);
	cout << "The table properties are" << endl;
	cout << "高度Height为" << cir_table.Height() << endl;
	cout << "面积Area为" << cir_table.Area() << endl;
	cout << "颜色color为" << cir_table.GetColor() << endl;
	return 0;
}