C++基础类知识

1. 默认构造，析构
2. 拷贝构造，移动构造
3. 拷贝赋值，移动赋值
4. 取值
5. 右值引用
6. 其它
• 基类的析构函数应使用virtual 关键字，保证子类的析构函数能够被正常调用
• 作为接口类，如果不是基类，应该用final关键字

 

// g++ testClass.cc -g -std=c++11 && ./a.out
#include <iostream>
#include <string.h>
using namespace std;

class MyStr final
{
private:
    char *name = NULL;
    int id;
    inline void MyStrncpy(char *dst, const char *src, size_t len) {
        if (dst != src) {
            strncpy(dst, src, len);
            dst[len] = '\0';
        }
    }
    inline void Reset() {
        id = 0;
        if (name) { 
            delete[] name; 
            name = NULL;
        }
    }
    inline void Clear() {
        id = 0;
        name = NULL;
    }
    inline void DeepCopy(const MyStr &other) {
        id = other.id;
        name = new char[strlen(other.name) + 1];
        MyStrncpy(name, other.name, strlen(other.name));        
    }
    inline void ShallowCopy(const MyStr &other) {
        id = other.id;
        name = other.name;      
    }
public:
    // 默认构造函数
    explicit MyStr():id(0),name(NULL) {
        cout << "构造: " << __func__ << endl;
    }
    // 构造函数
    explicit MyStr(int _id, char *_name) {
        cout << "普通构造： " << __func__ << endl;
        id = _id;
        name = new char[strlen(_name) + 1];
        MyStrncpy(name, _name, strlen(_name));
    }
    // 析构函数
    ~MyStr() {
        cout << "析构： " << __func__ << endl;
        Reset();
    }
    // 拷贝构造
    MyStr(const MyStr& other) {
        cout << "拷贝构造： " << __func__ << endl;
        DeepCopy(other);
    }
    // 移动构造
    MyStr(MyStr &&other) {
        cout << "移动构造： " << __func__ << endl;
        ShallowCopy(other);
        other.Clear();
    }
    // 拷贝赋值， rhs means right hand side value
    MyStr &operator=(const MyStr &rhs) {
        cout << "拷贝赋值： " << __func__ << endl;
        if (this != &rhs) {
            Reset();
            DeepCopy(rhs);
        }
        return *this;
    }
    // 移动赋值
    MyStr &operator=(MyStr &&rhs) {
        cout << "移动赋值： " << __func__ << endl;
        if (this != &rhs) {
            Reset();
            ShallowCopy(rhs);
            rhs.Clear();
        }
        return *this;
    }
};

int main()
{
    cout << "普通构造====================" << endl;
    MyStr str1(1, (char*)"aaa");
    cout << "普通构造====================" << endl;
    MyStr str2(2, (char*)"bbbb");
    cout << "拷贝赋值====================" << endl;
    str2 = str1;
    cout << "拷贝构造====================" << endl;
    MyStr str3 = str2;
    cout << "拷贝构造====================" << endl;
    MyStr str4(str2);
    cout << "移动构造====================" << endl;
    MyStr str5(std::move(str2));
    cout << "移动构造====================" << endl;
    MyStr str6 = std::move(str5);
    cout << "普通构造====================" << endl;
    MyStr str7(3, (char*)"ccccc");
    cout << "移动赋值====================" << endl;
    str7 = std::move(str6);
    return 0;
}