Rule of Three Part 1 & 2.

Rule of Three Part 1 & 2

Rule of Three Any object which manages memory needs: Custom Destructor
Custom Copy Constructor Custom Assignment Operator

Destructor Destructor : Special function called when object destroyed
Automatically called Almost never called by hand ~CLASSNAME()

Destructors Stack objects destroyed when leave scope:

Destructors Heap objects must be destroyed manually:

Cleaning Up Memory allocated by object = potential leak

Destructor Destructor used to clean up owned resources:
New in constructor  delete in destructor

Copy Constructor Every class has a default implicit copy constructor
Class::Class (const Class &other) Created invisibly and automatically

Copy Constructor Using copy constructor: p2 is copying p1

Copy Constructor Default works for simple objects: p1 p2 x: 4 y: 3

The Issue Default copy constructor for Polygon

The Issue Copies sides

The Issue Copies vertices pointer

The Issue Two objects now share one list of points

Shallow copy Shallow copy : duplicate pointers of an object
Copy shares memory with original

Deep copy Deep copy : duplicate memory owned by original
Copy gets own version of data

Copy Constructor Deep copy constructor Copy basic variables
Allocate own storage Copy data to it

Book Sample

Book Example Course class introduced in Ch 11

Book Example Constructor allocates array Destructor deletes

Book Example Book Ex11.20 copy constructor
Has typo – missing last 2 lines in book Should be:

Copy Constructor Deep copy recipe: Copy basic variables
Allocate own storage/resources Copy data from other to own storage

Copy Constructor Recipee
For Course:

Presentation on theme: "Rule of Three Part 1 & 2."— Presentation transcript: