Interview: String Class Constructor and Destructor Implementation

Given the String class definition:

class String
{
public:
String( const char *str = NULL); // General constructor
String(const String &another); // Copy constructor
~ String(); // Destructor
String & operater =(const String&rhs); // Assignment operator
private:
char *m_data; // Used to store the string
};

Attempt to implement the member functions of the class.

Answer:

// General constructor
String::String(const char *str){
    if ( str == NULL ) // This check is necessary because strlen throws an exception if the parameter is NULL.
    {
        m_data = new char[1] ;
        m_data[0] = '\0' ;
    }
    else
    {
        m_data = new char[strlen(str) + 1];
        strcpy(m_data,str);
    }
}

// Copy constructor
String::String(const String &another){
    m_data = new char[strlen(another.m_data) +1];
    strcpy(m_data,another.m_data);
} 

// Assignment operator
String& String::operator =(const String&rhs){
    if ( this == &rhs)
        return *this ;
    delete []m_data; // Delete original data, allocate new memory
    m_data = new char[strlen(rhs.m_data) + 1];
    strcpy(m_data,rhs.m_data);
    return *this ;
} 

// Destructor
String::~String(){
    delete []m_data ;
}