C++修炼之拷贝构造函数

class Date
{
public:
    //构造函数
    Date()
    {
        cout << "Date()" << endl;
    }
    //拷贝构造函数
    Date(const Date& d)
    {
        cout << "Date()" << endl;
        _year = d._year;
        _month = d._month;
        _day = d._day;
    }
    //析构函数
    ~Date()
    {
        cout << "~Date()" << endl;
    }
private:
    int _year = 0;
    int _month = 0;
    int _day = 0;
};

void TestDate()
{
    Date d1;
    //调用拷贝构造创建对象
    Date d2(d1);
}

class Date
{
public:
    //错误示例
    //如果这样写，编译器就会直接报错，但我们现在假设如果编译器不会检查，
    //这样的程序执行起来会发生什么
    Date(const Date d)
    {
        _year = d._year;
        _month = d._month;
        _day = d._day;
    }
private:
    int _year = 0;
    int _month = 0;
    int _day = 0;
};
void TestDate()
{
    Date d1;
    //调用拷贝构造创建对象
    Date d2(d1);
}

class Date
{
public:
    //构造函数
    Date(int year = 0, int month = 0, int day = 0)
    {
        //cout << "Date()" << endl;
        _year = year;
        _month = month;
        _day = day;
    }
    //未显式定义拷贝构造函数
    /*Date(const Date& d)
    {
        _year = d._year;
        _month = d._month;
        _day = d._day;
    }*/
    void print()
    {
        cout << _year << " - " << _month << " - " << _day << endl;
    }
private:
    int _year = 0;
    int _month = 0;
    int _day = 0;
};

void TestDate()
{
    Date d1(2023, 3, 31);
    //调用拷贝构造创建对象
    Date d2(d1);
    d2.print();
}

class stack
{
public:
    stack(int defaultCapacity=10)
    {
        _a = (int*)malloc(sizeof(int)*defaultCapacity);
        if (_a == nullptr)
        {
            perror("malloc fail");
            exit(-1);
        }
        _top =  0;
        _capacity = defaultCapacity;
    }
    ~stack()
    {
        cout << "~Stack()" << endl;
        free(_a);
        _a = nullptr;
        _top = _capacity = 0;
    }
    void push(int n)
    {
        _a[_top++] = n;
    }
    void print()
    {
        for (int i = 0; i < _top; i++)
        {
            cout << _a[i] << " ";
        }
        cout << endl;
    }
private:
    int* _a;
    int _top;
    int _capacity;
};

void TestStack()
{
    stack s1;
    s1.push(1);
    s1.push(2);
    s1.push(3);
    s1.push(4);
    s1.print();

    stack s2(s1);
    s2.print();
    s2.push(5);
    s2.push(6);
    s2.push(7);
    s2.push(8);
    s2.print();
}

class stack
{
public:
    stack(int defaultCapacity=10)
    {
        _a = (int*)malloc(sizeof(int)*defaultCapacity);
        if (_a == nullptr)
        {
            perror("malloc fail");
            exit(-1);
        }
        _top =  0;
        _capacity = defaultCapacity;
    }
    //用户自己定义拷贝构造函数
    stack(const stack& s)
    {
        _a= (int*)malloc(sizeof(int) * s._capacity);
        if (_a == nullptr)
        {
            perror("malloc fail");
            exit(-1);
        }

        memcpy(_a, s._a, sizeof(int) * s._capacity);
        _top = s._top;
        _capacity = s._capacity;
    }
    ~stack()
    {
        cout << "~Stack()" << endl;
        free(_a);
        _a = nullptr;
        _top = _capacity = 0;
    }
    void push(int n)
    {
        _a[_top++] = n;
    }
    void print()
    {
        for (int i = 0; i < _top; i++)
        {
            cout << _a[i] << " ";
        }
        cout << endl;
    }
private:
    int* _a;
    int _top;
    int _capacity;
};