Goals

• Specify the types of objects to create using the prototype instance and create new objects by copying this prototype.
• Create one instance of the class to use as the source for all future instances.
• The new operator is considered …

This pattern is ideal where you want to isolate your application from the implementation of the concrete classes. For example if you wanted to overlay Delphi's VCL with a common VCL layer for both 16 and 32 bit applications, you …

Abstract Factory classes are often implemented with Factory Methods, but they can also be implemented using Prototype. Abstract Factory might store a set of Prototypes from which to clone and return product objects.

• Factory Method: creation through inheritance.
• Prototype: creation …

An example of a design pattern An abstract factory in PHP

<?php
/*
 *  Abstract Factory classes
 */
 
abstract class DB_Abstraction_Factory {
    protected $settings = array();
    protected function __construct() {
        $this->settings = Settings::getInstance();
    }
 
    abstract public function createInstance();
}
 
class …

Goals

• We define an interface for creating an object, but let the subclasses decide which class to create. A factory method allows you to instantiate a class for subclasses.
• Definition of a "virtual" constructor.
• The new operator is harmful.

Problems …

An example of an abstract factory in the Python programming language

"""
Provide an interface for creating families of related or dependent
objects without specifying their concrete classes.
"""
 
import abc
 
 
class AbstractFactory(metaclass=abc.ABCMeta):
    """
    Declare an interface for operations that …

Discussion. "Think of object creation as a factory that spawns those same objects."

Here we assign object creation responsibilities to the factory object, and then use inheritance functions and virtual members to provide a "virtual constructor" capability. So there are …

The reasons

• Providing an interface for creating families of related or dependent objects without specifying their specific classes.
• Hierarchy that encapsulates: many possible "platforms" and building a set of "products".
• The new operator is considered harmful.

Problems

If an application …