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Our constructor function could be defined as:
String :: String (const char* s)
{
len = strlen(s);
text = new char[len+1];
}strcpy(text, s);
after computing the length of the string that s points to, the
constructor uses it to allocate enough space for a copy of a
string, before finally moving it into place.
To give back the space we need a destructor. If we
don't have one, then consider the problems of using the
String class within a procedure
void procedure ()
{
String S1("abc");
}........
when procedureis called the object S1 is created by the
constructor, but when the procedure returns the fields
textand lenofS1are removed, but the string "abc" itself
(that textpoints to) remains. This failure to return all the
memory acquired during procedure execution is called a
memory leak.
A destructor, a function that is called automatically
when an object ceases to exist, saves the day.
Constructors and destructors are matched pairs. Thus a
destructor is a member function just like a constructor and
has the same name, but with a tilde (~)pre-pended.
For example:
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