But in practice I've come to the idea it's a meaningless distinction if you're not going to bother to declare the types on your methods/functions.
Instances may be Strongly typed in Ruby. Methods are not. So you get almost none of the benefit. It's like Types only exist in Ruby to support Mixins and inheritance chains.
Prefer Composition over Inheritance right? But what if through Composition you effectively lost all your Type information? That's the issue Ruby presents.
Sure they are, just not all of them:
[].first('wat') # => TypeError: no implicit conversion of String into Integer
> Prefer Composition over Inheritance right? But what if through Composition you > effectively lost all your Type information? That's the issue Ruby presents.
This is mainly advocated because subclassing core classes (e.g. Array) can lead to weird behaviour. For example:
class MyArray < Array
end
m = MyArray.new([10, 20, 30])
p m.map { |number| number * 2 }.class # => Array
No. It is advocated because it produces simpler code in the long term in most cases. It is a quite different question to inheritance from core classes.
Though in hindsight you're right anyways. Methods define an implicit type for the arguments they operate over. It's just you don't know what it is without reading the whole method. Which I think gets to "expressiveness".