C + + Class Design 2 (class with pointer members)

Two class with pointer members (class String)

1. Test code (use effect)

int main () {    string S1 (),    string s2 ("Hello");          Constructor    String S3 (S1);               Copy construction    cout << S3 << Endl;    s3 = S2;                     Copy Assignment    cout << S3 << Endl;}

2 Big Three (three kinds of special functions)

Class String{public:    String (const char* CSTR = 0);    String (const string& str); Parameters are references to objects of the same type, copy constructs     string& operator= (const string& str);//Copy Assignment    ~string ()//destructor    char* Get_c _str () const{        return m_data;    } Private:    char* m_data;};

2.1 ctor & Dtor (Construction and destruction)

inlinestring::string (const char* CSTR = 0) {    if (CStr) {        m_data = new Char[strlen (CStr) +1];        strcpy (M_DATA,CSTR);     }    else{   //Unspecified length         m_data = new char[1];        *m_data = ' + ';    }} Inlinestring::~string () {    

2.2 Class with pointer must have copy ctor (copy construction) and copy op (copy assignment)

Deep copy and shallow copy

Deep copy:

inlinestring::string (const string& str) {    m_data = new Char[strlen (str.m_data) + 1];  Direct access to another object's private data                                                //Can be UF meta-interpretation     strcpy (m_data, str.m_data);}

Copy Assignment function:

Idea: If the right side is copied to the left, the steps are empty to the left, the same space is assigned to the right, and the copy is completed.

inlinestring& string::operator= (const string& str) {    if (this = = &str) {  //Detect self-assignment, not just efficiency issues         return *this;  If not tested, may cause the behavior undefined, see explanation    }    delete[] m_data;    Clear left     m_data = new char[strlen (str.m_data) + 1];//Open space     strcpy (m_data, str.m_data);//Complete copy     

Summary: A class with pointer variables, be sure to re-copy the construction, copy assignment and destructor!

C + + Class Design 2 (class with pointer members)