C++字符串不能在类中连接

#include <iostream>
#include <cstring>

class MyClass {
public:
    void stringConcatenation() {
        char str1[50] = "Hello";
        char str2[] = " World!";
        strcat(str1, str2);
        std::cout << str1 << std::endl;
    }
};

int main() {
    MyClass obj;
    obj.stringConcatenation();
    return 0;
}

#include <iostream>
#include <string>

class MyClass {
public:
    void stringConcatenation() {
        std::string str1 = "Hello";
        std::string str2 = " World!";
        std::string result = str1 + str2;
        std::cout << result << std::endl;
    }
};

int main() {
    MyClass obj;
    obj.stringConcatenation();
    return 0;
}