Modern deep copy writing and modern deep copy writing

Modern deep copy writing and modern deep copy writing

The modern method of deep copy is simpler than the traditional method. That is, an intermediate object tmp is created. Its _ str Pointer Points to s. _ str, exchange tmp. after _ str and _ str, _ str points to s. _ str: if the copy is out of the scope, tmp will automatically call its destructor, releasing the memory that the original _ str points to, which also achieves our desired effect.

For example:

# Include <iostream> using namespace std; class String {public: String (char * str = "") // strlen (NULL) is not allowed ): _ str (new char [strlen (str) + 1]) {strcpy (_ str, str);} String (const String & s): _ str (NULL) {String tmp (s. _ str); swap (_ str, tmp. _ str);} String & operator = (const String & s) {if (this! = & S) {String tmp (s. _ str); swap (_ str, tmp. _ str);} return * this ;}~ String () {delete [] _ str;} private: char * _ str ;};

Of course, the value assignment operator overload here can be further optimized:

String & operator = (String s) // optimization (s cannot be referenced, otherwise it will change the value of the real parameter) (Here s is a copy of the real parameter) {swap (_ str, s. _ str); return * this ;}