C++ 第二章封装

封装

我该有的我该做的

构造函数与析构函数

构造/析构函数	使用方式
默认构造函数	People a;
People(const People &a)	拷贝构造，与=不等价
People(string name);	People a(“bug”)
~People()	无

class People {
public:
    People(){}
    People(string name) {//有参构造
        this->name = name;
    }
    
    ~People() {
        cout << "destructor" << endl;
    }
    string name;
    //int *arr;
};

int main() {
    People b("fangsong");
    People a = string("string");
    //a.arr[9] = 12
    cout << a.name << endl;
    return 0;
}

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;

class People {
public :
    People() {}
    //People() = default; //  //隐藏规则变为显示规则，易于代码维护
   //People() = delete;
    People(string name) {
        cout << "param constructor" << endl;
        this->name = name;
    }
    People(int x) {
        cout << "int param constructor" << endl;
        this->x = x;
    }
    People(const People &a) {
        cout << "copy constructor" << endl;
        this->name = a.name;
        this->x = a.x;
    }
    
    void operator=(const People &a) {
        cout << "operator =" << endl;
        this->name = a.name;
        this->x = a.x;
        return ;
    }

    ~People() {
        cout << "destructor" << endl;
    }
    string name;
    int x;
};

void incr(int &a) {
    a += 1;
    return ;
}

int add(People a, People b) {
    return a.x + b.x;
}

int main() {
    int n = 7;
    incr(n);
    cout << n << endl;
    cout << add(4, 5) << endl;
    People a("hug");
    People b = string("hug");
    People c(543);
    People d = 678;
    cout << a.name << endl;
    cout << b.name << endl;
    cout << c.x << endl;
    cout << d.x << endl;
    c = 987;
    cout << c.x << endl;
    d = string("duanchenyang");
    cout << d.name << endl;
    People e = a;
    cout << e.name << endl;
    cout << e.x << endl;
    c = a;
    cout << c.name << endl;
    cout << c.x << endl;
    return 0;
}

类属性方法

static 类成员，类方法

类的成员与方法

class People {
public:
	void say(string word);
	void run(location &loc)
	///
	static void is_valid_height(double height);
	/
private:
	static int totle;
	string __name;
	Day __birthday;
	double __height;
	double __wright;
};

类属性与类方法中，类属性可以记录类对象的个数，类方法中不能访问this指针;

const方法

不去修改对象中的值

const类型对象只能调用const类型方法

修饰后只能类const访问

class People {
public:
	void say(string word);
	void run(location &loc)
	///
	string &name() const()
	///
	static void is_valid_height(double height);
private:
	static int totle;
	string __name;
	Day __birthday;
	double __height;
	double __wright;
};

类属性与const代码演示

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;

class Point {
public :
    Point() {
        cout << "constructor : " << this << endl;
        Point::total_cnt += 1;
    }
    Point(const Point &a) : Point() {
        cout << "copy constructor : " << this << endl;
        this->x = a.x;
        this->y = a.y;
    }
    Point(double z) : Point() {
        cout << "convert constructor : " << this << endl;
        this->x = 99, this->y = 99;
    }
    Point(int x, int y) : Point() {
        cout << "param constructor : " << this << endl;
        this->x = x;
        this->y = y;
    }

    void operator=(const Point &a) {
        cout << "operator= : " << this << endl;
        this->x = a.x, this->y = a.y;
        return ;
    }
    void set(int x, int y) {
        this->x = x;
        this->y = y;
    }
    void seek() const {
        seek_cnt += 1;
        cout << x << " " << y << endl;
    }

    void s() const{
        cout << seek_cnt << endl;
    }

    static int T() { return Point::total_cnt; }//类承成员方法

    ~Point() {
        cout << "destructor : " << this << endl;
        Point::total_cnt -= 1;
    }

private:
    int x, y;
    mutable int seek_cnt = 0;
    static int total_cnt;//类方法成员属性
};
int Point::total_cnt = 0;

void test() {
    Point a;
    cout << Point::T() << endl;
    return ;
}
int main() {
    Point a;
    cout << a.T() << endl;
    test();
    Point b;
    cout << b.T() << endl;
    Point c(3, 4);
    cout << c.T() << endl;
    Point d(3.4);
    cout << d.T() << endl;
    c = 5.6;
    cout << c.T() << endl;
    cout << &a << endl;
    cout << &b << endl;
    cout << &c << endl;
    cout << &d << endl;
    d.seek();
    c.seek();
    const Point e(6, 7);
    e.seek();
    e.seek();
    e.seek();
    e.seek();
    e.s();
    return 0;
}

深拷贝与浅拷贝

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;

class A {
public :
    A() {
        this->arr = new int[100];
    }
    A(const A &obj) : x(obj.x), y(obj.y) {
        this->arr = new int[100];
        memcpy(this->arr, obj.arr, sizeof(int) * 100);
    }
    int *arr;
    int x, y;
};

int main() {
    A a;
    a.x = 3, a.y = 6;
    a.arr[0] = 123;
    A b = a;
    b.arr[0] = 456;
    cout << a.arr[0] << " " << b.arr[0] << endl;
    cout << b.x << " " << b.y << endl;
    b.x = 6;
    cout << a.x << " " << a.y << endl;
    cout << b.x << " " << b.y << endl;
    return 0;
}

类型转换

#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;
class BigInt{
    public :
    BigInt() {}
    BigInt(int x) {
        num.push_back(x);
        process_digit();
    }
    friend ostream &operator<<(ostream &, const BigInt &);
    private:
    vectornum;
    void process_digit() {
        for(int i = 0; i < num.size(); i++) {
            if(num[i] < 10) continue;
            if(i + 1 == num.size())num.push_back(0);
            num[i + 1] = num[i]/10;
            num[i] %= 10;
        }
        return;
    }
};

ostream &operator<<(ostream &out, const BigInt &a) {
    for(int i = a.num.size() - 1; i >= 0; i--) {
        out << a.num[i];
    }
    return out;
}

void func(BigInt a) {
    cout << "func : " << a << endl;
}

int main() {
    BigInt a;
    a = 1234;
    cout << a << endl;
    func(5670);
    return 0;
}

运算符重载

#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;

namespace haizei {
    
class istream{
public :
    istream &operator>>(int &n){
        std::cin >> n;
        return *this;
    }
private:

};

class ostream {
public :
    ostream &operator<<(int &n) {
        std::cout << n;
        return *this;
    }
    ostream &operator<<(const char *msg) {
        std::cout<< msg;
        return *this;
    }
private:

};
istream cin;
ostream cout;
};

haizei::ostream &operator<<(haizei::ostream &out, double &z) {
    std::cout << z;
    return out;
}

ostream &operator+(ostream &out,const int &z){
    out << z;
    return out;
}

int main() {
    int n, m;
    haizei::cin >> n >> m;
    haizei::cout << n <<" "<< m << "n";
    double k = 5.6;
    haizei::cout << k << "n";
    cout + 8 + 9 + 10;
    cout + k;
    (((((cout + 8 )<< " ") + 9) << " ") + 10) << endl;
    return 0;
}


#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;

class Point{
public:
    Point() : __x(0), __y(0){}
    Point(int x, int y) : __x(x), __y(y){}
    int x() const {return __x;}
    int y() const {return __y;}
    Point operator+(const Point &a) {
    
    return Point(x() + a.x(), y() + a.y());
    }
    Point &operator+=(const Point &a) {
        __x += a.x();
        __y += a.y();
        return *this;
    }
    Point &operator++(){
        __x +=1;
        __y +=1;
        return *this;
    }
    Point operator++(int) {
        Point temp(*this);
        __x += 1;
        __y += 1;
        return temp;
    }
private:
    int __x, __y;
};

ostream &operator<<(ostream &out, const Point &a) {
    cout << "Point (" << a.x() << "," <
    Point a(4, 5), b(3, 4), c(1, 1);
    cout << a << endl;
    cout << b << endl;
    cout << c << endl;
    cout << a << " " << b << endl;
    cout << a + b << endl;
    cout << ++(c += b) << endl;
    cout << c << endl;
    cout << c++ << endl;
    cout << c << endl;
    int n = 6, m = 7;
    (n += m) ++;
    cout << n << endl;
    return 0;
}




#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;

class A{
public:
    A() {
        arr = new int[10];
    }
    A(const A &a) : A() {
        for(int i = 0; i < 10; i++) {
            this->arr[i] = a.arr[i];
        }
        this->x = a.x;
        this->y = a.y;
        return;
    }
    int x, y;
    int *arr;
};

class B{
public :
    B() : obj(nullptr) {
        arr = new int[10];
        arr[3] = 9973;
    }
    B(A *obj) : B() {
        this->obj = obj;
    }
    int operator() (int a, int b) {
        return a + b;
    }
    int &operator[](int ind) {
        return arr[ind];
    }
    void operator[](const char *msg) {
        cout << msg << endl;
        return;
    }
    A *operator->() {
        return obj;
    }
    A &operator*() {
        return *obj;
    }
    ~B() {
        delete arr;
    }
private:
    int *arr;
    A *obj;
};

ostream &operator <<(ostream &out, const A &a) {
    out << "A（" << a.x << " ," << a.y << ")" << endl;
    return out;
}

int main() {
    B add;
    cout << add(3, 4) << endl;
    cout << add[3] << endl;
    add[3] = 8876;
    cout << add[3] << endl;
    add["hello world"];

    A a, b(a);
    a.x = 67, a.y = 99;
    B p = &a;
    cout << p->x << " " << p->y << endl;
    cout << *p << endl;
    
    a.arr[3] = 9973;
    b.arr[3] = 6687;
    cout << a.arr[3] << endl;
    cout << b.arr[3] << endl;
    return 0;
}

C++ 第二章 封装

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C++ 第二章封装