c++&Qt_day05

作业1

题目

仿 String 类 ，写一个 MyString 类

效果

代码

main.c

#include 

#include "myString.h"

using namespace std;

void printStr(const char *msg, MyString &str);

int main(int argc, char const *argv[])
{
    // 无参构造
    MyString s0;

    // 有参构造
    MyString s1("hello");

    // 拷贝构造
    MyString s2 = "world!";
    MyString s3 = s2;

    cout << "s0 = " << s0 << endl;
    cout << "s1 = " << s1 << endl;
    cout << "s2 = " << s2 << endl;
    cout << "s3 = " << s3 << endl;

    cout << "=========================" << endl;
    // 拷贝赋值
    s3 = s1;
    cout << "s3 = s1              ==> s3 = " << s3 << endl;

    s3 = "ok";
    cout << "s3 = \"ok\"            ==> s3 = " << s3 << endl;

    // +重载
    s3 = s1 + " " + s2;
    cout << "s3 = s1 + \" \" + s2;  ==> s3 = " << s3 << endl;

    // +=重
    s3 += "###";
    cout << "s3 += \"###\"          ==> s3 = " << s3 << endl;
    s3 += s1;
    cout << "s3 += s1;            ==> s3 = " << s3 << endl;

    // []
    cout << "s4[1] = " << s3[1] << endl;

    cout << "=========================" << endl;
    // ==
    cout << "s1 = " << s1 << endl;
    cout << "s2 = " << s2 << endl;
    cout << boolalpha << endl;
    cout << "s1 == s2  ==> " << (s1 == s2) << endl;

    // !=
    cout << "s1 != s2  ==> " << (s1 != s2) << endl;

    // <
    cout << "s1 < s2  ==> " << (s1 < s2) << endl;

    // >
    cout << "s1 > s2  ==> " << (s1 > s2) << endl;

    // <=
    cout << "s1 <= s2  ==> " << (s1 <= s2) << endl;

    // >=
    cout << "s1 >= s2  ==> " << (s1 >= s2) << endl;

    // 转换c风格
    cout << "=========================" << endl;
    const char *s5 = s1.c_str();
    cout << "c风格字符串 s5 = " << s5 << endl;

    return 0;
}

/**
 * @brief    打印字符串
 * @param    msg 自定义的信息
 * @param    str 要打印的字符串对象
 * @return
 */
void printStr(const char *msg, MyString &str)
{
    cout << msg << " = ";
    // 判空
    if (str.isEmpty()) {
        cout << str.at(0) << endl;
        return;
    }
    // 按长度遍历
    for (int i = 0; i < str.size(); i++) {
        // 按下标输出
        cout << str.at(i);
    }
    cout << endl;
}

MyString.h

#ifndef _MY_STRING_H_
#define _MY_STRING_H_

#include 

using namespace std;

class MyString
{
   public:
    MyString();
    MyString(const char *s);
    MyString(const char *&s);                                               // 拷贝构造
    MyString(const MyString &other);                                        // 拷贝构造
    ~MyString();                                                            // 析构
    MyString &operator=(const char *s);                                     // 拷贝赋值
    MyString &operator=(const MyString &other);                             // 拷贝赋值
    friend ostream &operator<<(ostream &output, const MyString &myString);  // 输出重载
    friend istream &operator>>(istream &input, const MyString &myString);   // 输入重载
    friend const MyString operator+(const MyString &l, const MyString &r);  // +重载
    friend MyString &operator+=(MyString &l, const MyString &r);            // +=重载
    friend bool operator==(const MyString &l, const MyString &r);           // ==重载
    friend bool operator!=(const MyString &l, const MyString &r);           // !=重载
    friend bool operator<(const MyString &l, const MyString &r);            // <重载
    friend bool operator>(const MyString &l, const MyString &r);            // >重载
    friend bool operator<=(const MyString &l, const MyString &r);           // <=重载
    friend bool operator>=(const MyString &l, const MyString &r);           // >=重载
    char &operator[](int pos);                                              // []重载
    bool isEmpty() const;                                                   // 判空
    int size() const;                                                       // 长度
    const char *c_str() const;                                              // MyString字符串转换为c风格
    char &at(int pos) const;                                                // 按下标获取字符

   private:
    char *_str;
    int _size;
};

#endif  //_MY_STRING_H_

MyString.cpp

#include "myString.h"

#include 

/**
 * @brief    无参构造
 * @param    无
 * @return   无
 */
MyString::MyString() : _size(0), _str(new char) { strcpy(_str, ""); }

/**
 * @brief    有参构造
 * @param    s 字符串
 * @return   无
 */
MyString::MyString(const char *s)
{
    this->_size = strlen(s);
    this->_str = new char[this->_size + 1];
    strcpy(this->_str, s);
}

/**
 * @brief    拷贝构造
 * @param    s 字符串
 * @return   无
 */
MyString::MyString(const char *&s)
{
    this->_size = strlen(s);
    this->_str = new char[this->_size + 1];
    strcpy(this->_str, s);
}

/**
 * @brief    拷贝构造
 * @param    other 目标对象
 * @return   无
 */
MyString::MyString(const MyString &other)
{
    if (this != &other) {
        this->_size = other._size;
        this->_str = new char[other._size + 1];
        strcpy(this->_str, other._str);
    }
}

/**
 * @brief    拷贝赋值
 * @param    s 目标字符串
 * @return   源对象
 */
MyString &MyString::operator=(const char *s)
{
    this->_size = strlen(s);
    delete (this->_str);
    this->_str = new char[this->_size + 1];
    strcpy(this->_str, s);

    return *this;
}

/**
 * @brief    拷贝赋值
 * @param    other 目标对象
 * @return   源对象
 */
MyString &MyString::operator=(const MyString &other)
{
    if (this != &other) {
        this->_size = other._size;
        delete (this->_str);
        this->_str = new char[this->_size + 1];
        strcpy(this->_str, other._str);
    }

    return *this;
}

/**
 * @brief    析构函数
 * @param    无
 * @return   无
 */
MyString::~MyString() { delete (this->_str); }

/**
 * @brief    判空
 * @param    无
 * @return   ture表示空   false表示非空
 */
bool MyString::isEmpty() const { return (this->_size == 0) ? true : false; }

/**
 * @brief    获取长度
 * @param    无
 * @return   长度
 */
int MyString::size() const { return this->_size; }

/**
 * @brief    将MyString类型转换为c风格字符串
 * @param
 * @return
 */
const char *MyString::c_str() const { return this->_str; }

/**
 * @brief    按下标获取字符
 * @param    pos 下标
 * @return   下标对应字符
 */
char &MyString::at(int pos) const { return this->_str[pos]; }

/**
 * @brief    输出运算符重载
 * @param    output 输出流对象
 * @param    myString 要重载输出的对象
 * @return   输出流对象
 */
ostream &operator<<(ostream &output, const MyString &myString)
{
    output << myString._str;
    return output;
}

/**
 * @brief    输入运算符重载
 * @param    input 输入流对象
 * @param    myString 要重载输出的对象
 * @return   输入流对象
 */
istream &operator>>(istream &input, const MyString &myString)
{
    input >> myString._str;
    return input;
}

/**
 * @brief    加法运算符重载
 * @param    l 左值
 * @param    r 右值
 * @return   零时变量
 */
const MyString operator+(const MyString &l, const MyString &r)
{
    MyString ret = l;
    strcat(ret._str, r._str);
    return ret;
}

/**
 * @brief    加等运算符重载
 * @param    l 左值
 * @param    r 右值
 * @return   零时变量
 */
MyString &operator+=(MyString &l, const MyString &r)
{
    // 备份
    char tmp[1024];
    strcpy(tmp, l._str);

    // 重新开辟
    delete (l._str);
    l._str = new char[l.size() + r.size() + 1];

    // 赋值
    strcpy(l._str, tmp);
    strcat(l._str, r._str);

    return l;
}

/**
 * @brief    ==运算符重载
 * @param    l 左值
 * @param    r 右值
 * @return   相等返回true 不等返回false
 */
bool operator==(const MyString &l, const MyString &r) { return !strcmp(l._str, r._str); }

/**
 * @brief    !=运算符重载
 * @param    l 左值
 * @param    r 右值
 * @return   不等返回true 相等返回false
 */
bool operator!=(const MyString &l, const MyString &r) { return strcmp(l._str, r._str); }

/**
 * @brief    <运算符重载
 * @param    l 左值
 * @param    r 右值
 * @return   左值较小返回true 左值较大返回false
 */
bool operator<(const MyString &l, const MyString &r) { return (l._str - r._str) < 0 ? true : false; }

/**
 * @brief    >运算符重载
 * @param    l 左值
 * @param    r 右值
 * @return   左值较大返回true 左值较小返回false
 */
bool operator>(const MyString &l, const MyString &r) { return (l._str - r._str) > 0 ? true : false; }

/**
 * @brief    <=运算符重载
 * @param    l 左值
 * @param    r 右值
 * @return   左值<=右值返回true 左值>右值返回false
 */
bool operator<=(const MyString &l, const MyString &r) { return (l._str - r._str) <= 0 ? true : false; }

/**
 * @brief    >=运算符重载
 * @param    l 左值
 * @param    r 右值
 * @return   左值>=右值返回true 左值<右值返回false
 */
bool operator>=(const MyString &l, const MyString &r) { return (l._str - r._str) >= 0 ? true : false; }

/**
 * @brief    []运算符重载
 * @param    pos 下标
 * @return   下标字符
 */
char &MyString::operator[](int pos) {
    return this->_str[pos];
}