Component\Util\Singleton

Component\Util\Singleton is a simple-to-use PHP component that provides the Singleton (and Registry of Singletons a.k.a. Multiton) creational design pattern.

Table of Contents (ToC)

• Introduction
• Features
• Requirements
• Usage
• Installation
• Testing
• Contributing
• Credits
• License

Introduction

Singleton is a creational design pattern and defined as follows:

"Ensure a class only has once instance, and provide a global access point to it."

-- E. Gamma, et al. Design Patterns: Elements of Reusable Object-Oriented software. Westford: Addison-Wesley, 1995.

Component\Util\Singleton contains of two traits:

• The trait SingletonTrait: A generic implementation of the Singleton creational design pattern.
• The trait MultitonTrait: A generic implementation of the Registry of Singletons a.k.a. Multiton creational design pattern.

The generic implementations as traits make this component reusable (see the section Features below).

Features

• Allows to pass parameters to the static Creation Method getInstance(). The parameters are passed to the protected constructor of the class using the component.
• Allows a number of unlimited classes to use the component.
  • A class which uses the SingletonTrait (or MultitonTrait) can still inherit from another class.
  • A class which extends a class using the SingletonTrait (or MultitonTrait) is a new Singleton (or Multiton). Therefore the component supports inheritance.
• Disallows cloning and serializing of a Singleton (or Multiton) instance.
• Disallows overriding of the methods getInstance(), __clone and __wakeup.
• Follows the naming conventions for the Singleton design pattern (offers a static Creation Method getInstance()).
• Artifacts tested with both static and dynamic test procedures:
  • Dynamic component tests (unit and integration tests) implemented with PHPUnit.
  • Static code analysis performed using the following tools:
    • PHP_CodeSniffer: Style Checker
    • PHP Mess Detector (PHPMD): Code Analyzer
    • PHP Depend: Code Metrics
    • phpcpd: Copy/Paste Detector (CPD)
    • phpdcd: Dead Code Detector (DCD)
    • SensioLabs Security Checker: Security Checker
  • Continuous Integration (CI) using the following web services:
    • Scrutinizer CI
    • SensioLabsInsight
    • Coveralls
    • VersionEye
    • Depending
    • Waffle
• Provides a Packagist package which can be installed using the dependency manager Composer. Click here for the package on Packagist.
• Provides a complete Application Programming Interface (API) documentation generated with the documentation generator Sami. Click here for the API documentation.
• Follows the following "standards" from the PHP Framework Interoperability Group (FIG). PSR stands for PHP Standards Recommendation:

  • PSR-0: Autoloading Standards

    Aims to provide a standard file, class and namespace convention to allow plug-and-play code.

  • PSR-1: Basic Coding Standard

    Aims to ensure a high level of technical interoperability between shared PHP code.

  • PSR-2: Coding Style Guide

    Provides a Coding Style Guide for projects looking to standardize their code.

  • PSR-4: Autoloader

    A more modern take on autoloading reflecting advances in the ecosystem.

• Follows the Semantic Versioning (SemVer) specification version 2.0.0.

Requirements

Production

• PHP >= 5.4
• Composer
• florianwolters/component-util-reflection
• florianwolters/component-core-stringutils

Development

• PHPUnit
• phpcpd
• phpdcd
• PHP_CodeSniffer
• PHP Mess Detector (PHPMD)
• Sami
• SensioLabs Security Checker
• php-coveralls

Installation

Component\Util\Singleton should be installed using the dependency manager Composer.

Composer is a tool for dependency management in PHP. It allows you to declare the dependent libraries your project needs and it will install them in your project for you.

The Composer installer can be downloaded with php.

php -r "readfile('https://getcomposer.org/installer');" | php

This will just check a few PHP settings and then download composer.phar to your working directory. This file is the Composer binary. It is a PHAR (PHP archive), which is an archive format for PHP which can be run on the command line, amongst other things.

To resolve and download dependencies, run the install command:

php composer.phar install

If you are creating a component that relies on Component\Util\Singleton, please make sure that you add Component\Util\Singleton to your component's composer.json file:

{
    "require": {
        "florianwolters/component-util-singleton": "0.3.*"
    }
}

Usage

The best documentation for Component\Util\Singleton are the unit tests, which are shipped in the package.

Additional documentation can be found in the official Wiki of the project.

Testing

phpunit

Contributing

Please see CONTRIBUTING for details.

Credits

• Florian Wolters
• All Contributors

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see https://gnu.org/licenses/lgpl.txt.