#include <cstring>
#include <iostream>

class String {
public:
    explicit String(const char* cstr = nullptr){//初始化
        if (cstr) {
            pstr = new char[strlen(cstr) + 1];
            len = strlen(cstr);
            strcpy(pstr, cstr);
        } else {
            pstr = new char[1];
            len = 0;
            *pstr = '\0';
        }
    }
    String(const String& str){//拷贝构造
        pstr = new char[str.len + 1];
        len = str.len;
        strcpy(pstr, str.pstr);
    }
    String(String&& str) noexcept { //移动构造(右值
        if (str.pstr != nullptr) {
            pstr = str.pstr;
            str.pstr = nullptr;
            len = str.len;
        }
    }
    String& operator=(const String& str){ //拷贝复制
        if (this == &str) {
            return *this;
        }
        delete[] pstr;
        pstr = new char[str.len + 1];
        len = str.len;
        strcpy(pstr, str.pstr);
        return *this;
    }
    String& operator=(String&& str) noexcept {//移动赋值(右值
        if (this != &str) {
            delete[] pstr;
            pstr = str.pstr;
            str.pstr = nullptr;
            len = str.len;
        }
        return *this;
    }
    ~String(){
        delete []pstr;
        len = 0;
    }
    int size() const{
        return len;
    }
    char* get_c_str() const {
        return pstr;
    }
private:
    char* pstr;
    int len;
};

简单版，其他如 输入输出运算符，[] 等等查看

https://www.cnblogs.com/zhizhan/p/4876093.html