design-patterns-api

    0.4.20 • Public • Published

    design-patterns-api

    Catalog of Design Patterns as Interface classes (by means of mixin-interface). This catalog provides the 23 original ("Gang of Four") patterns, as well as further patterns (e.g. Null Object).

    ATM this framework provides 20 out of the 23 'Original Patterns' described by the Gang of Four in their 1995's book (Elements of Reusable Object-Oriented Software). There are further design patterns described later (e.g. Patterns of Enterprise Architecture Application written by Martin Fowler).

    Your feedback (via GitHub) is welcome especially to report bugs or design issues, request for features or enhancements and contribute to the 'religious' aspects of this project, like which patterns are in fact Antipatterns or if it depends on the context (e.g. Singleton, Service Locator...).

    Note about Design Issues

    • Craft a proposal for each pattern: there are many references about Design Patterns. My proposals should be not be taken as reference but more as an ongoing work (for which your feedback is welcome). Thus I advise you to study by yourself the references (I have gathered some of them in the References paragraph) to check it they fits your learning curve and your own design issues.
    • Resolve name conflicts across patterns: in the references, it happens that participant names (and operation names as well) are shared across patterns. In my proposals, I resolved these name conflicts either by mining in the references or by adding parent interface classes (e.g. IElement, _IAction, ICoreComponent...).

    Release 0.4.20 changelog

    • Impact of Log feature refactoring (please find reference documentation here):
      • Implementation of Log feature redesigned and moved from mixin-interface to mixin-interface-api.
      • New Log API is MxI.$Log.write() (previously MxI.$System.log()) and MxI.$Log.addSink() (to set the target of trace requests).
      • Thus this package now directly depends from mixin-interface-api (and no more from mixin-interface).

    Release 0.4.16 changelog

    • Impacts where forgotten: updates in README and 'createProduct()' in 'LoggerFactory' must be replaced by 'createElement()'

    Release 0.4.15 changelog

    • Impact of a refactoring in 'design-patterns-core-api' dependency (deletion of 'IProduct' and then update 'its dependents so that they depend on 'IElement' instead)

    Roadmap

    • Documentation upgrades: UML class diagram and implementation sample for each pattern

    Preliminary notes

    Naming convention: for any given interface class, its name is written with PascalCase convention (e.g. IAbstractFactory) and its source code uses snake_case convention (e.g. i_abstract_factory.js)

    Why ...args ? Thanks to the rest parameter feature of javascript es6 (...args), most interface services accept optional and variable number of arguments.

    What is the purpose of xxx_id arguments ? This is a design choice motivated by 2 design intents. The first is when the service call is propagated (e.g. 'request_id' argument is propagated by Adapter when IAdapter.request() calls IAdaptee.specificRequest()). The second is to avoid counterproductive class proliferation by using xxx_id argument as a way to make the call more specific (e.g. 'request_id' argument when calling IHandler.handleRequest() within the Chain Of Responsability pattern)

    Creational patterns

    Abstract Factory

    Interface classes: IAbstractFactory and IElement.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Abstract Factory.
    Abstract Factory UML model

    Factory Method

    Interface classes: I_Creator and IElement.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Factory Method.

    Builder

    Interface classes: IBuilder and IElement.
    Detailed description: BlackWasp - Builder design pattern.

    Singleton

    Interface class: MxI.$ISingleton.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Singleton.

    Behavioral patterns

    Observer

    Interface classes: IObserver and IObservable.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Observer.
    Observer UML model

    Iterator

    Interface classes: IIterator and ICollection.
    Detailed description: Tutorials Point - Design Patterns: Iterator pattern.

    State

    Interface classes: IState and IStateContext.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - State.

    Chain of Responsability

    Interface classes: IHandler and IRequest.
    Detailed description: OOODesign - Chain of Responsability.

    Visitor

    Interface classes: IVisitor and IElement.
    Detailed description: Tutorials Point - Design Patterns: Visitor pattern.

    Memento

    Interface classes: IMemento, IOriginator and ICareTaker.
    Detailed description: Tutorials Point - Design Patterns: Memento pattern.

    Strategy

    Interface classes: IStrategy and IStrategyContext.
    Detailed description: Tutorials Point - Design Patterns: Strategy pattern.

    Command

    Interface classes: ICommand, IInvoker and IReceiver.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Command.

    Template Method

    Interface class: ITemplateMethod.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Template Method.

    Mediator

    Interface classes: IMediator, IColleague and IRequest.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Mediator.

    Structural patterns

    Bridge

    Interface class: IImplementor.
    Refer to Enginyeria del Software I - Curs 2006-2007 - Bridge.

    Adapter

    Interface classes: IAdapter and IAdaptee.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Adapter.

    Facade

    Interface class: IFacade.
    Detailed description: Tutorials Point - Design Patterns: Memento pattern.

    Decorator

    Interface classes: IDecorator and ICoreComponent.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Decorator.

    Composite

    Interface classes: IComponent, IComposite and ILeaf.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Composite.

    Proxy (new)

    Interface classes: ISubject and IProxy.
    Detailed description: Enginyeria del Software I - Curs 2006-2007 - Proxy.

    Beyond "Gang of Four" patterns

    Null Object

    Interface class: MxI.$INullObject.
    Detailed description: Tutorials Point - Design Patterns: Null Object pattern.

    Developer's Guide

    How to implement a Design Pattern

    A given Design Pattern is composed of one or more participants, this is very much like Role(s) in a play. Within design-patterns-api project, each participant is implemented as an interface classs. Thus, in order to implement a Design Pattern you must implement the interface class(es). Please refer to How to code an Implementation class in the documentation of mixin-interface-api package.

    Code Sample: LoggerFactory

    LoggerFactory shows how to delegate the instanciation of a Logger (a more flexible way to log traces than console.log) by implementing the Abstract Factory design pattern.

    See source code of LoggerFactory here. It is demonstrated in Unit Test.

    How to run the Unit Test

    Step 1: Install Prerequisite Tools

    Install NodeJS and Git

    Step 2: Clone the 'design-patterns-api' repository locally

    Open a command shell then enter the following commands:

    git clone git://github.com/Echopraxium/design-patterns-api
    cd design-patterns-api
    npm update
    

    Step 3: Run the Unit Test

    Now enter the following command:

    node test.js
    

    You should get this kind of output (please find here the full output):

    ============================================================
    ======== Unit Test for 'design-patterns-api' package =======
    ============================================================
    1. Creational Patterns
    ----------
    1.1. Abstract Factory
    Demonstrate 'Abstract Factory' Design pattern by changing DefaultLogger:
    ==> Logger is now 'arrow_prefix_logger_0'
    [17:11:42 PM] Logger is now 'timestamp_prefix_logger_0'
    [0] Logger is now 'count_prefix_logger_0'
    ...
    ===================== End of Unit Test =====================
    

    References

    Install

    npm i design-patterns-api

    DownloadsWeekly Downloads

    48

    Version

    0.4.20

    License

    MIT

    Last publish

    Collaborators

    • echopraxium