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Design Pattern PrototypeAuthor:

Vladislav AkulichQA automation

Coherent Solutions

Minsk 2014

OverviewPrototype is a creational pattern.

This pattern encapsulate the knowledge about which classes a system users, but they hide the details of how the instances of these classes are created and put together.

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Intent

Specify the kind of objects to create using a prototypical instance, and create new objects by copying this prototype.

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Applicability• When the classes to instance are

specified at run-time, for example, by dynamic loading

• To avoid building a class hierarchy of factories that parallels the class hierarchy of products

• When instance of a class can have one of only a few different combinations of state.

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UML Diagram

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Participant• Prototype–Declares an interface for cloning itself

• Concrete Prototype– Implements an operation for cloning itself

• Client–Creates a new object by asking a prototype

to clone itself

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Consequences• Adding and removing products at run-time• Specifying new objects by varying values• Specifying new objects by varying structure• Reduced subclassing• Configuring an application with classes

dynamically

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Copy options

• Deep Copy (implementation in user code), but in some languages exist functions which do it

• Simple object clone (standard function MemberwiseClone())

Simple Copy • C#

• Ruby

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Deep CopyC# Ruby

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Related PatternsPrototype and Abstract Factory are

competing patterns. They can also be used together, however. An Abstract Factory might store a set prototypes from which to clone and return product objects.

Designs that make heavy use of the Composite and Decorator patterns often can benefit from Prototype as well.

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Code example

Simple projects on:• C#• Ruby

Useful books• C# 3.0 Design Patterns• Gang of Four Design Patterns 4.0• Code Complete Second Edition By Steve

Mcconnell

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Useful links• Ruby Best Practices:

http://blog.rubybestpractices.com/posts/gregory/059-issue-25-creational-design-patterns.html

• Prototype design pattern C++ example: http://www.ccplusplus.com/2012/01/prototype-design-pattern-c-example.html

• Wikipedia: http://ru.wikipedia.org/wiki/%D0%9F%D1%80%D0%BE%D1%82%D0%BE%D1%82%D0%B8%D0%BF_(%D1%88%D0%B0%D0%B1%D0%BB%D0%BE%D0%BD_%D0%BF%D1%80%D0%BE%D0%B5%D0%BA%D1%82%D0%B8%D1%80%D0%BE%D0%B2%D0%B0%D0%BD%D0%B8%D1%8F)

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Thanks

Vladislav Akulich

ISsoft QA Engineer

VladislavAkulich@coherentsolutions.com

ISsoft Solutions

www.issoft.by