Constructor (object-oriented programming): Difference between revisions

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In [[class-based programming|class-based]] [[object-oriented programming]], a '''constructor''' (abbreviation: '''ctor''') in a [[Class (computer programming)|class]] is a special type of [[subroutine]] called to [[object creation|create an object]]. It prepares the new object for use, often accepting [[argument]]s that the constructor uses to set required [[member variable]]s.

A constructor resembles an [[method (computer science)|instance method]], but it differs from a method in that it has no explicit [[return type]], it is not implicitly [[inheritance (object-oriented programming)|inherited]] and it usually has different rules for scope modifiers. Constructors often have the same name as the declaring [[class (computer science)|class]]. They have the task of [[initialization (computing)|initializing]] the object's [[data member]]s and of establishing the [[Class invariant|invariant of the class]], failing if the invariant is invalid. A properly written constructor leaves the resulting [[object (computer science)|object]] in a ''valid'' state. [[Immutable object]]s must be initialized in a constructor.