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Marc Scholten:
Accidental Complexity Caused By Service Containers In The PHP World
May 24, 2016 @ 11:25:30

In this post to his site Marc Scholten talks about something that's become a side effect of using the inversion of control design pattern in PHP applications (specifically related to dependency injection): added accidental complexity.

Modern PHP development favors the use of inversion of control to keep software more configurable and flexible. This leads to the problem that one now has to create a big graph of objects to use the application. As a solution to avoid redundant setup code, service containers like the symfony2 dependency injection component are used.

The goal of a service container is to centralize the construction of big object graphs. [...] Simple, right? Actually it’s not. Commonly used service containers are complex solution for simple problems.

He illustrates with an example using the Symfony services container, a piece of the framework that allows the definition of dependency relationships via a YAML formatted file. While this configuration seems simple enough, he points out that more complex dependencies (ones that could easier be set via a "set" method) become more difficult to define when limited by the service container config structure. He also points out that it makes static analysis of the code much more difficult with dependencies being dynamically fetched from the container instead of directly related. He offers an alternative to this complex container setup, however: a simple method (or methods) inside of a factory class that creates the objects, injects the required dependencies. This makes it much easier to call from the service container instance and configuration and even a "create container" call to set all of the dependencies up at once. He ends the post with some advantages of this approach and a takeaway or two to keep in mind when managing your object dependencies.

tagged: complexity service container accidental configuration simplex complex example symfony

Link: https://www.mpscholten.de/software-engineering/2016/05/21/accidental-complexity-caused-by-service-containers-in-the-php-world.html