The Decree Design Pattern
calebhearth.com
calebhearth.com
I wrote this up partially to codify some of how I've been explaining it to folks ad-hoc, but also to share with the broader community and get input on this way of extracting processes in Ruby/Rails projects.
I have quite often wanted the ability to easily collect the arguments to a function call together in a structure with the function itself, and defer the execution of the method. I want a closure essentially but with the ability to reflect and inspect the arguments and function, potentially make changes, and execute it later.
Of course the only real way to do this in most languages is to make every single thing i want to do a single-function class with public "argument" members. But that messes with the structure of the code.
It would be really nice to have some syntactic sugar for extracting a class for function calls and their arguments.
The decree pattern seems similar the solution I've described above but avoided implementing because it sounds crazy.
https://stackoverflow.com/questions/3188048/how-to-bind-argu...
Player would be a namespace. It would be a module with no or limited code. Within it would be Controller, Model or the agent noun modules that take call: Creator, Inporter, Mailer - the “er” words indicate there will be a single call function.
We broke from the standard Rails directory structure. All the code for Player would be in one directory - including views.
Feature-slicing (directory per feature) vs Component-slicing (models, views, controllers each have their own directory regardless of which feature they contribute to).
In the ProcessPayment example he says the pattern is good because it lets you split the construction of the payment from its execution.
Soooo why not have a Payment class with a process method? Am I missing something?
It dawn on me that the latter is precisely what people at Java do, and I've reached the conclusion that this way of writing software is enforced by Java developers who realized they needed to learn Ruby because their job prospects are better, and are simply retrofitting what they used to do in a new programming language.
Extracting important business behaviour into objects allows applying OO (ie, powerful despatch rules) where it is valuable.
Subtyping your model to achieve many of these possible usecases would give poor design results.
For example, if payment processing were in Payment.process() the Payment entity would need to be subtyped or composed for any of 1) a different payment gateway, 2) a sales tax in a new jurisdiction, 3) a new confirmation, or 4 a new payment flow. Having all that in your model entity is probably wrong.
Simple behaviour is fine in the model, major business TN usually not.
There's nothing at all wrong with having, say, a PaymentGateway and SalesTax classes and composing them with Payment in whatever way makes sense given their interdependent relationships. Code that has real life analogs to objects tends to be much cleaner, in fact.
I used it to leverage OOP from non-OOP languages (like C).
An SDK that I wrote in 1994, using it, was still in use, when I left the company, in 2017.
You have a dequeue class, the stack and queue inherit dequeue. But dequeue is a subtype of stack and queue.
About union, could i say an abstract class is a union (implicitly) of all its subclasses ?