Factory method pattern: Difference between revisions

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{{Short description|Object-oriented software design pattern}}

In [[object-oriented programming]], the '''factory method pattern''' is a [[software design pattern|design pattern]] that uses factory methods to deal with the problem of [[object creation|creating objects]] without having to specify their exact [[class (computer programming)|classes]]. Rather than by calling a [[Constructor (object-oriented programming)|constructor]], this is accomplished by invoking a factory method to create an object. Factory methods can be specified in an [[Interface (object-oriented programming)|interface]] and implemented by subclasses or implemented in a base class and optionally [[method overriding|overridden]] by subclasses. It is one of the 23 classic design patterns described in the book ''[[Design Patterns]]'' (often referred to as the "Gang of Four" or simply "GoF") and is subcategorized as a [[creational pattern]].{{sfn|Gamma|Helm|Johnson|Vlissides|19941995|page=107}}

==Overview==

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== Examples ==

This [[C++1423]] implementation is based on the pre C++98 implementation in the ''[[Design Patterns]]'' book.{{sfn|Gamma|Helm|Johnson|Vlissides|19941995|page=122}}{{Which one|date=August 2024}}

<syntaxhighlight lang="c++">

import std;

#include <iostream>

#include <memory>

enum class ProductId {MINE, YOURS};

// defines the interface of objects the factory method creates.

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public:

void print() {

std::cout << println("this=" << this << "{} print MINE\n", this);

}

};

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public:

void print() {

std::cout << println("this=" << this << "{} print YOURS\n", this);

}

};