问创建了自己的字符串类--带有重载赋值运算符和析构函数的错误

EN

String::~String()
{
delete [] mStr;
mStr = nullptr;
}

    String tempBuffer;

    //Store entire worth of potions
    tempBuffer = "Platinum: ";
    tempBuffer += currencyBuffer[0];
    tempBuffer += "\nGold: ";
    tempBuffer += currencyBuffer[1];
    tempBuffer += "\nSilver: ";
    tempBuffer += currencyBuffer[2];
    tempBuffer += "\nCopper: ";
    tempBuffer += currencyBuffer[3];

    mCost = tempBuffer;

String &String::operator=(const String & rhs)
{
//Check for self-assignment
if(this != &rhs)
{
    //Check if string is null
    if(rhs.mStr != nullptr)
    {
        //Delete any previously allocated memory
        delete [] this->mStr;

        //Deep copy
        this->mStr = new char[strlen(rhs.mStr) + 1];
        strcpy(this->mStr, rhs.mStr);
    }
    else
        this->mStr = nullptr;
}

//Return object
return *this;
}

String &String::operator+=( String rhs)
{
//Check for self-assignment
if(this != &rhs)
{
    //Convert to cString
    char * buffer = rhs.c_str();

    //Find length of rhs
    int length = strlen(buffer);

    //Allocate memory
    char * newSize = new char[length + 1];

    //Copy into string
    strcpy(newSize, buffer);

    //Concatenate
    strcat(this->mStr, newSize);

    //Deallocate memory
    delete [] newSize;

}

//Return object
return *this;
}

String::String(const String & copy)
:mStr()
{
*this = copy;
}

String::String(char * str)
{
//Allocate memory for data member
mStr = new char[strlen(str) + 1];

//Copy str into data member
strcpy(mStr, str);
}

String::String(char ch)
{
//Assign data member and allocate space
mStr = new char[2];

//Assign first character to the character
mStr[0] = ch;

//Assign second character to null
mStr[1]= '\0';
}