Constructor (object-oriented programming): Difference between revisions

Revision as of 16:32, 14 December 2014

Revision as of 16:52, 14 December 2014

Line 266:

</source>

On returning objects from functions or passing objects by value, the objects copy constructor will be called implicitly, unless [[return value optimization]] applies.

In C++ the copy constructor is called implicitly when class objects are returned from a method by return mechanism or when class objects are passed by value to a function. C++ provides a copy constructor if the programmer does not. The default copy constructor ONLY makes member-wise copy or shallow copies. For deep copies an explicit copy constructor that makes deep copies is required. For a class to make deep copies, the three methods below must be provided.

C++ implicitly generates a default copy constructor which will call the copy constructors for all base classes and all member variables unless the programmer provides one, explicitly deletes the copy constructor (to prevent cloning) or one of the base classes or member variables copy constructor is deleted or not accessible (private). Most cases calling for a customized '''copy constructor''' (e.g. [[reference counting]], [[deep copy]] of pointers) also require customizing the '''destructor''' and the '''copy assignment operator'''. This is commonly referred to as the [[Rule of three (C++ programming)|Rule of three]].

# Copy constructor

# Overloading of assignment operator.

# A destructor.

The above is called rule of three in C++. If cloning of objects is not desired in C++ then copy constructor must be declared private.

=== F# ===