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In class-based, object-oriented programming, a constructor (abbreviation: ctor) is a special type of function called to create an object. It prepares the new object for use, often accepting arguments that the constructor uses to set required member variables.
Perl 5.6.1 and newer support autovivification of file and directory handles. [3] Calling open() on an undefined variable will set it to a filehandle. According to perl561delta, "[t]his largely eliminates the need for typeglobs when opening filehandles that must be passed around, as in the following example:
To effect the creation of a new object which is a shallow duplicate of y, the feature twin is used. In this case, one new object is created with its fields identical to those of the source. The feature twin relies on the feature copy, which can be redefined in descendants of ANY, if needed. The result of twin is of the anchored type like Current.
In object-oriented programming, a factory is an object for creating other objects; formally, it is a function or method that returns objects of a varying prototype or class [1] from some method call, which is assumed to be new. [a] More broadly, a subroutine that returns a new object may be referred to as a factory, as in factory method or ...
The method Print in class Box, by invoking the parent version of method Print, is also able to output the private variables length and width of the base class. Otherwise, these variables are inaccessible to Box. The following statements will instantiate objects of type Rectangle and Box, and call their respective Print methods:
According to Design Patterns: Elements of Reusable Object-Oriented Software: "Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory method lets a class defer instantiation to subclasses." [2] Creating an object often requires complex processes not appropriate to include within a composing object.
The term closure is often used as a synonym for anonymous function, though strictly, an anonymous function is a function literal without a name, while a closure is an instance of a function, a value, whose non-local variables have been bound either to values or to storage locations (depending on the language; see the lexical environment section below).
In computer programming, lazy initialization is the tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed.