There has been sentiment that ruby's modules enable composition, but this is not the case. Composition describes a "has-a" relationship, whereas (in ruby) when a class includes a module, it creates an is-a relationship.
There are four basic forms of modules in ruby, some good, some not so good.
| Superclass.for(obj) # => The concrete subclass instance you wanted |
At the 2004 Ruby Conference, Jamis Buck had the unenviable task to explain Dependency Injection to a bunch of Ruby developers. First of all, Dependency Injection (DI) and Inversion of Control (IoC) is hard to explain, the benefits are subtle and the dynamic nature of Ruby make those benefits even more marginal. Furthermore examples using DI/IoC are either too simple (and don’t convey the usefulness) or too complex (and difficult to explain in the space of an article or presentation). I once attempted to explain DI/IoC to a room of Java programmers (see onestepback.org/articles/dependencyinjection/), so I can’t pass up trying to explain it to Ruby developers.
Thanks goes to Jamis Buck (the author of the Copland DI/IoC framework) who took the time to review this article and provide feedback.
| # lib/mygem/cli.rb | |
| require "mygem" | |
| require "mygem/configuration" | |
| module MyGem | |
| class CLI | |
| def actual_cli_method(x,y) | |
| MyGem.config = configuration(opts) | |
| MyGem::StuffDoer.new(x).go(y) |
| require 'psych' | |
| class WorseScanner < Psych::ScalarScanner | |
| def parse_time(s) | |
| s | |
| end | |
| end | |
| s = "---\nf: 2001-02-29T01:02:03-03:00" # Note this day doesn't exist. |