C++ String 类

源码

#include <iostream>
#include <cstring>

#pragma warning(disable : 4996)  // for MSVC

class String
{
public:
    String(const char* str = nullptr) {
        if (str == nullptr) {
            data_ = new char[1];
            *data_ = '\0';
            std::cout << "Default constructor" << std::endl;
        }
        else {
            int length = strlen(str);
            data_ = new char[length + 1];
            std::strcpy(data_, str);
            std::cout << "Pass argument constructor" << std::endl;
        }
        
    }
    
    String(const String& other) {
        int length = strlen(other.data_);
        data_ = new char[length + 1];
        std::strcpy(data_, other.data_);
        std::cout << "Copy constructor" << std::endl;
    }

    String& operator=(const String& other) {
        if (this != &other) {
            if (!data_) delete[] data_;
            int length = strlen(other.data_);
            data_ = new char[length + 1];
            strcpy(data_, other.data_);
        }
        std::cout << "Copy assignment" << std::endl;
        return *this;
    }

    ~String() {
        delete[] data_;
        std::cout << "Destructor" << std::endl;
    }

    String(String&& other) noexcept {
        data_ = other.data_;
        other.data_ = nullptr;
        std::cout << "Move constructor" << std::endl;
    }

    String& operator=(String&& other) noexcept {
        if (this != &other) {
            delete[] data_;
            data_ = other.data_;
            other.data_ = nullptr;
        }
        std::cout << "Move assignment" << std::endl;
        return *this;
    }

private:
    char* data_;
};


int main()
{  
    // 测试：默认构造
    String s1;

    // 测试：传参构造
    String s2("Hello world!");

    // 测试：拷贝构造
    String s3(s1);

    // 测试：移动构造
    String s4(std::move(s3));

    // 测试：拷贝赋值
    String s5;
    s5 = s4;

    // 测试：移动赋值
    String s6;
    s6 = std::move(s5);

    return 0;
}

运行结果

Result