About deep copy and shallow copy

Understanding of deep copies and shallow copies:

Shallow copy: Is the same space that is shared between the copied object and the Copy object, that is, the pointer of two objects points to the same space.

Deep copy: The Copy object and the Copy object have their own space, the Copy object will open a new space, and then copy the object copied down.

Here are the implementations of deep and shallow copies

Class String

{

Public

Traditional notation

string& operator= (const string& s)//operator overloading

{

if (This! = &s)

{

/*delete[] _STR; First release the _STR, then open up space, then copy

_str = new Char[strlen (S._STR) + 1];

strcpy (_str, S._STR); * *

char* tmp = new Char[strlen (S._STR) + 1];

strcpy (TMP, S._STR); First use the temporary object tmp to open up space, when the string is copied to

Delete[] _STR; TMP, then release _STR, and finally assign the TMP address to _STR

_STR = tmp;

}

return *this;

}

String (char* str = "")//constructor

: _str (new Char[strlen (str) + 1])

{

strcpy (_str, str);

}

String (const string& s)//copy constructor

: _str (New Char[strlen (S._STR) + 1])

{

strcpy (_str, S._STR);

}

~string ()//destructor

{

if (_STR)//If _STR is not empty, use to release _str

{

Delete[] _STR;

}

}

Modern notation

String (const string& s)//copy constructor

: _str (NULL)

{

String tmp (S._STR); Creates a temporary object that copies a string to a temporary object, TMP

Swap (_STR, TMP._STR); Exchange _STR and Tmp._str pointer values, at which point TMP points to null

and _str points to the string

}

string& operator= (const string& s)//operator overloading

{

if (&s! = this)

{

String tmp (S._STR); Method Ibid.

Swap (_STR, TMP._STR);

}

return *this;

}

Overloading optimization for string& operator= (String s)//operator

{

Swap (_STR, S._STR); The above function is optimized, and a copy is made during the incoming object.

So the direct exchange of pointer values is possible.

return *this;

}

Private

char * _STR;

};

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About deep copy and shallow copy