C + + Object-oriented Programming note 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 Function    String S3 (S1);               // Copy Construction    cout << S3 << Endl;     = S2;                     // Copy Assignment    cout << S3 << Endl;}

2 Big Three (three kinds of special functions)

classstring{ Public: String (Const Char* CStr =0); String (Conststring& str);//arguments are references to objects of the same type, copy constructsstring&operator=(Conststring& str);//Copy Assignment~string ()// Destructors    Char* GET_C_STR ()Const{        returnm_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{//length not specifiedM_data =New Char[1]; *m_data =' /'; }}inlinestring::~String () {Delete[] m_data;} 

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) {    newchar1] ;  // direct access to the private data                                                of another object //      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=(Conststring&str) {    if( This= = &str) {//Detecting self-assignment is not just a matter of efficiency        return* This;//if not tested, may cause undefined behavior, see explanation    }    Delete[] m_data;//Clear leftM_data =New Char[Strlen (Str.m_data) +1];//Open Spacestrcpy (M_data, str.m_data);//Complete Copy    return* This} 

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

C + + Object-oriented Programming note 2 (Class with pointer members)