解决方案是将std::string的所有操作都显式地公开给新包装器，并将它们重定向到std::string的对应操作，示例代码如下：

class MyString {
public:
    // construct from const char*
    MyString(const char* str) : str_(str) {}

    // copy constructor
    MyString(const MyString& other) : str_(other.str_) {}

    // move constructor
    MyString(MyString&& other) noexcept : str_(std::move(other.str_)) {}

    // copy assignment
    MyString& operator=(const MyString& other) {
        str_ = other.str_;
        return *this;
    }

    // move assignment
    MyString& operator=(MyString&& other) noexcept {
        str_ = std::move(other.str_);
        return *this;
    }

    // conversion to std::string
    operator const std::string&() const noexcept {
        return str_;
    }

    // length() operation
    size_t length() const noexcept {
        return str_.length();
    }

    // find() operation
    size_t find(const MyString& substr, size_t pos = 0) const noexcept {
        return str_.find(substr.str_, pos);
    }

    // substr() operation
    MyString substr(size_t pos = 0, size_t len = std::string::npos) const {
        return MyString(str_.substr(pos, len).c_str());
    }

    // insert() operation
    MyString& insert(size_t pos, const MyString& str) {
        str_.insert(pos, str.str_);
        return *this;
    }

    // erase() operation
    MyString& erase(size_t pos, size_t len = std::string::npos) {
        str_.erase(pos, len);
        return *this;
    }

    // append() operation
    MyString& operator+=(const MyString& str) {
        str_.append(str.str_);
        return *this;
    }

private:
    std::string str_;
};