【公有继承】继承自string的MyString

#include <cstdlib>
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
class MyString : public string
{
public:
    MyString() : string() {}
    MyString(const MyString &ms) : string(ms) {}
    MyString(const char *s) : string(s) {}
    MyString(const string &s) : string(s) {}
    MyString operator()(int start, int len) { return substr(start, len); }
};
int main()
{
    MyString s1("abcd-"), s2, s3("efgh-"), s4(s1);
    MyString SArray[4] = {"big", "me", "about", "take"};
    cout << "1. " << s1 << s2 << s3 << s4 << endl;
    s4 = s3;
    s3 = s1 + s3;
    cout << "2. " << s1 << endl;
    cout << "3. " << s2 << endl;
    cout << "4. " << s3 << endl;
    cout << "5. " << s4 << endl;
    cout << "6. " << s1[2] << endl;
    s2 = s1;
    s1 = "ijkl-";
    s1[2] = 'A';
    cout << "7. " << s2 << endl;
    cout << "8. " << s1 << endl;
    s1 += "mnop";
    cout << "9. " << s1 << endl;
    s4 = "qrst-" + s2;
    cout << "10. " << s4 << endl;
    s1 = s2 + s4 + " uvw " + "xyz";
    cout << "11. " << s1 << endl;
    sort(SArray, SArray + 4);
    for (int i = 0; i < 4; i++)
        cout << SArray[i] << endl;
    //s1的从下标0开始长度为4的子串
    cout << s1(0, 4) << endl;
    //s1的从下标5开始长度为10的子串
    cout << s1(5, 10) << endl;
    return 0;
}

• 调用父类构造函数的写法
• 不需要自己实现更多的运算符重载以及析构函数之类的，因为继承了父类所有的成员函数和成员变量，当调用这些重载过的运算符的时候，就直接使用父类继承下来的函数和变量。