Decoupling is hard work, especially when taken to extremes – as the team of Diablo II did when they decoupled the whole rendering stack of the original game from the rest of the engine to reuse both independently. Today I learned that Diablo II Resurrected is a true remaster: new 3D graphics, but the engine hasn’t changed. In an interview with Eurogamer, Rob Gallerani pointed out that
Say you have a view component. You can control which subcomponents it displays for maximum reuse. One day, you end up configuring the available effects, or actions, of the view component. Let’s say it’s something like this, a made-up example: The delete case with its associated value sticks out a bit.
Here’s a short definition of the two terms: Cohesion is about how well elements within a module belong together and serve a common purpose. Coupling is about how much one module depends or interacts with other modules. Thus, cohesion is an intra-module concern whereas coupling cuts across modules [aka inter-module].
(Devopedia)
Reactive, declarative code is sequentially cohesive: you have a sequence of events and reactions to events, and it’s pieces are tied together real close. The processing chain itself is then a function or feature of the app. The chain of operators is a thing itself; the step-by-step transformation is then reified into a sequence in one place: it has a beginning, an end, a sequential order of steps.
This blog post was originally meant as a reply to the ReSwift issue “Any way to control the priority of subscription callbacks?” – If you find asking yourself this question, this should help. This implementation detail is hidden by design. If you find yourself wanting to affect the order of subscription callbacks, there’s a concept of a sequence waiting to be extracted somehow. Or, the other way around: if you want to affect the order, your design is wonky.