This is another excerpt from my latest book, which is currently part of Manning’s Early Access Program. Take 37% off Object Design Style Guide by entering fccnoback into the discount code box at checkout at manning.com.

Make sure to read part 1 first.

Create read models directly from their data source

Instead of creating a StockReport model from PurchaseOrderForStock objects, we could go directly to the source of the data, that is, the database where the application stores its purchase orders. If this is a relational database, there might be a table called purchase_orders, with columns for purchase_order_id, product_id, ordered_quantity, and was_received. If that’s the case, then StockReportRepository wouldn’t have to load any other object before it could build a StockReport object; it could make a single SQL query and use it to create the StockReport, as shown in Listing 11).

I’m happy to share with you an excerpt of my latest book, which is currently part of Manning’s Early Access Program. Take 37% off Object Design Style Guide by entering fccnoback into the discount code box at checkout at manning.com.

Chapter 7: Dividing responsibilities

We’ve looked at how objects can be used to retrieve information, or perform tasks. The methods for retrieving information are called query methods, the ones that perform tasks are command methods. Service objects may combine both of these responsibilities. For instance, a repository (like the one in Listing 1) could perform the task of saving an entity to the database, and at the same time it would also be capable of retrieving an entity from the database.

“Can you make a query bus with SimpleBus?” The question has been asked many times. I’ve always said no. Basically, because I didn’t build in the option to return anything from a command handler. So a handler could never become a query handler, since a query will of course have to return something.

I’ve always thought that the demand for a query bus is just a sign of the need for symmetry. If you have command and query methods, then why not have command and query buses too? A desire for symmetry isn’t a bad thing per se. Symmetry is attractive because it feels natural, and that feeling can serve as design feedback. For instance, you can use lack of symmetry to find out what aspect of a design is still missing, or to find alternative solutions.

With excerpts from the documentation

I have worked with symfony 1, Symfony 2+, Zend Framework 1, Zend Expressive, but never with Laravel. Until now. My partner was looking for a way to learn PHP and building web applications with it. Most of my own framework knowledge is related to Symfony, so my initial plan was to find a Symfony course for her. However, Jeffrey Way’s Laracasts also came to mind, and I thought it would be an interesting learning experience for us both if Laravel would be the framework of choice in this matter. It turned out to be a good idea. My partner is making good progress, and I get to see what Laravel is all about. We have a lot of fun together, finding out how it works, or what you’re supposed to be doing with it.

This week I attended and spoke at the Newcrafts conference in Paris. The following is a mix of notes and personal observations I wanted to share, centered around some of the talks I saw there.

Romeu Romera: Bourdieu’s Social theory and our work in tech

I had never attended a talk by Romeu before. I really enjoyed this one. Somehow I already knew that he uses a mindmap to support his talk. I thought he would use an existing mind map to navigate through the talk, but it turned out he was creating one during the talk. For me personally, a slide deck helps to keep track of the story, and it helps me remember all the different topics I need to talk about. Not so much for Romeu, who knew exactly what he was going to talk about, and didn’t seem to forget to mention any important part, or make important connections.

With a foreword by Ross Tuck

Today I’ve released the revised edition of my latest book “Style Guide for Object Design”. Over the past few weeks I’ve fixed many issues, smaller and larger ones. Ross Tuck and Laura Cody have read the manuscript and provided me with excellent feedback, which has helped me a lot to get the book in a better shape. I added many sections, asides, and even an extra chapter, because some topics deserve more detail and background than just a few paragraphs. Oh, and Ross wrote the kindest of forewords to kick off the book. It’s available in the free sample of the book.

You say "convention over configuration;" I hear "ambient information stuck in someone's head." You say "configuration over hardcoding;" I hear "information in a different language that must be parsed, can be malformed, or not exist."

— Paul Snively (@paul_snively) March 2, 2019

Dependency injection is very important. Dependency injection containers are too. The trouble is with the tools, that let us define services in a meta-language, and rely on conventions to work well. This extra layer requires the “ambient information” Paul speaks about in his tweet, and easily lets us make mistakes that we wouldn’t make if we’d just write out the code for instantiating our services.

Cyrille Martraire: Domain modeling towards First Principles

This was a talk from the first day, but it required some more processing before writing about it. Cyrille is one of my favorite speakers. He’s fast, funny and brings a lot of interesting topics to the table. So many that it’s sometimes hard to keep following his train of thought, and writing down some notes at the same time.

A central concept from his talk was what he called the waterline between IT and the business. In a traditional scenario, developers get provided with “work” on a case-by-case basis. They don’t learn about the general idea or plan, or even the vision, goal or need that’s behind the “work item”. They just have to “implement” it. It leads to badly designed code. But it also leads to the wrong solutions being delivered. If only developers could have talked with the people who actually have the problem for which they build the solution. Maybe there’s another problem behind it, or maybe the business has provided the developer with a solution, instead of a problem. To higher the waterline means to get more involved with the customers and users, to understand their problems, and work together on a solution. Make sure you get involved.

Eric Evans: Keynote (“Language in Context”)

Starting out with the basics (words have meaning within a context; when we make the boundary of this context explicit we end up with a bounded context), Eric discussed two main topics: the Big Ball of Mud, and bounded contexts in the context (no pun intended) of microservices.

Legacy applications are always framed in a negative way, as if it’s something to get away from. Personally, I’ve come to enjoy them a lot. However, there will always be the urge to work around legacy code. The Bubble Context (PDF) can be a great way of creating a new model that works well next to the already existing models. To keep a safe buffer between the new and the old model, you could build an Anti-Corruption Layer (ACL). A fun thing Eric mentioned is that the buffer works in two directions. The ACL also allows the old model to keep functioning without being disturbed by all the new things that are going on in the Bubble Context.

All of a sudden it became book-writing season. It began in August when I started revising my second book, “Principles of Package Design”. Apress had contacted me about adopting it, and they didn’t want to change a lot about it. However, the book was from 2015 and although I had aimed for it to be “timeless”, some parts needed an update. Furthermore, I had happily pressed the “Release” button back then, but it’s the same as with software development: the code you wrote last year, you wouldn’t approve of today.