Basic Principles

TYPO3 comes with an impressive variety of available extensions. As usual with Open Source projects, these extensions have been written by various programmers. Extensions are used in all sorts of projects: some are written for use in small organizations or even in private, others are developed in big teams in the context of major projects. As a newbie writing your first extension, you may struggle with some first-time problems concerning TYPO3, as many big projects are based on homemade Frameworks. So style and architecture of today's extensions are quite heterogeneous. Hence, it is often very difficult to extend or modify existing extensions for your own projects. Before you can do that, you will have to wrap your head around the development style of the respective author or team of authors.

It's one of the aims of Extbase to reduce this inconsistency in extensions. Approved paradigms of programming lead to fast success for newbies and protect developers from having to deal with complex database queries or potential security holes like SQL-Injections or XSS-Attacks. Using Extbase, small Extensions as well as big projects can be realized in a well-structured way.

Extbase is based on four interconnected and complementary paradigms, which we would like to present in this chapter. You'll encounter these during the whole project cycle, from planning to realization and maintenance of your extension:

  • Object-Oriented Programming (OOP): describes how to encapsulate associated real world aspects to abstract objects in a software
  • Domain-Driven Design (DDD): The goal of this approach is to transcribe terms, rules and actions of the problem at hand in an adequate way.
  • Model-View-Controller (MVC): This programming paradigm leads to a clear isolation of data, control of actions, and logic of interaction.
  • Test-Driven Development (TDD): This approach is a basic technique for generating code which is stable, resilient to errors and legible - and therefore maintainable.

Each of these four paradigms are well known in professional software development and more or less widespread. This results in a big advantage when using Extbase. Until now an expert in developing TYPO3 extensions was mainly an expert in the usage (and bypassing) of the application programming interface (API) of TYPO3. In contrast, Extbase will demand additional knowledge and skills in domains that are useful and effective far beyond the TYPO3 Community. Thus, you can rely on an extensive record of experience in the form of books, forums or personal contacts – an important aspect of the future of TYPO3.

Knowledge in Object-Oriented Programming, Domain-Driven Design and the MVC-paradigm is essential for working with extbase. Knowledge of Test-Driven Development is not absolutely necessary for understanding nor using extbase. Nevertheless we would like to warmly recommend this development technique.