In a new post to his site Tomas Votruba comes back to a topic he posted about previously - the collector pattern - and provides a simpler, more introductory look at the pattern and what it's useful for.

I wrote Why is Collector Pattern so Awesome a while ago, but I got feeling and feedback that it's way too complicated.

The pattern itself is simple but put in framework context, it might be too confusing to understand. That's why we look on collector pattern in minimalistic plain PHP way today.

He uses a calculator example help explain the use of the pattern, starting with a simple class that calculates the price of a product + VAT. He then shows a few examples of how it could grow over time as business requirements change. He refactors the class to make it easier to add in these one-off changes by setting them all as "calculators' in a calculator collection. He provides the code examples for this refactor and an example of it in use.

In a new post to his site Tomas Votruba shares some of his thoughts about why he thinks the Collector pattern is so awesome. The Collector pattern is one of many design patterns that can be used to create well-structured applications.

I already wrote about Collector pattern as one we can learn from Symfony or Laravel. But they're so useful and underused I have need to write a more about them.

Yesterday I worked on Rector and needed an entry point to add one or more Rectors by user.

He then goes through the process he followed during the refactor and some of the questions he asked:

• Add a Provider?
• Use Expression Language?
• Does Collector Scale?
• Add Tagging?

He finishes the post with one last thought about git history and how it should "tell the story" of the refactoring.

Marc Moreram has posted a guide on his site to using event listeners as collectors in Symfony 2 based applications. He shows how to hook into the eventing system and both gather events fired (matching your criteria) and view the current collection.

Some of my concerns during the last couple of years have been how to collect data from all installed bundles using available tools in Symfony packages. I say concerns because I don’t really know if is there a tool for that. Some people have told me that the EventDispatcher component can do this work greatly, but then I have the same question once and again… is this component designed for such?

He uses an example of gathering mmoreram.wake_up events from his codebase, triggered when it "wakes up". He shows how to create a simple class for the event with a "rested" value. He modifies this to set up an array of "feelings" inside the event and a method to add new instances to the internal array. Finally he shows how to dispatch an event of the mmoreram.wake_up type and access the resulting set of "feelings" directly from the event.