News Feed
Sections




News Archive
Looking for more information on how to do PHP the right way? Check out PHP: The Right Way

PHPMaster.com:
Constructors and the Myth of Breaking the Liskov Substitution Principle
October 08, 2012 @ 11:53:13

On PHPMaster.com there's a new post in a series looking at the SOLID design principles in PHP development. In this new tutorial they try to dispel the myth that constructors break the Liskov Substitution Principle ("L" in "SOLID").

Rants aside, the morale of the story can be boiled down to the following: "Object construction is not part of the contract honored by its implementers". It's easier to grasp concepts by example rather than reading dull theory, so in this article I'll be demonstrating from a practical standpoint how the implementation of different constructors down the same hierarchy isn't a violation of the Liskov Substitution Principle, which is a reason why you shouldn't fall into the temptation of tainting your interfaces with constructors.

He illustrates the point with a simple PDO class that implements a "DatabaseAdapterInterface" interface that defines its own constructor that follows the defaults of the PDO extension. He goes on and changes the constructor for the class a bit to take in an array of config options rather than the DSN/User/Password combo. Inside of this constructor, those values are then taken and pushed into PDO to create the connection. He also suggests one other solution - the injection of a connection object ("ConnectionDefinition") into the constructor instead of the configuration directly.

0 comments voice your opinion now!
solid development liskov substitution principle tutorial constructor


blog comments powered by Disqus

Similar Posts

PHPMaster.com: Implementing PSR-3 with log4php

Kevin Waterson's Blog: Introduction to PHP Regex

Mushfiqsimple Blog: Getting Started with MongoDb with PHP

PHPMaster.com: What's New in Zend Framework 2

Freek Lijten's Blog: SOLID - The O is for Open Closed Principle


Community Events





Don't see your event here?
Let us know!


bugfix release tips opinion introduction package voicesoftheelephpant symfony api language deployment list laravel series interview library podcast install framework community

All content copyright, 2014 PHPDeveloper.org :: info@phpdeveloper.org - Powered by the Solar PHP Framework