Question

I am new to Ruby. Is there a way to write a single ‘def Array/Range/Hash’ with a method_missing that will work for all Ranges, Arrays and Hash i.e. all Enumerables? For e.g. the following should work:

[1..5].Sum()  
[1,2,3,5].Sum()  
{'x' => 1, 'y' = 4}.Sum()  

Sum() is our custom method defined inside method_missing. As of now, I have written three different functions that handle method_missing for Array, Range and Hash separately.

Answer 1

You can define method_missing for all Enumerables by opening Enumerable module and adding an instance method to it:

module Enumerable
  def method_missing *args
    puts 'hi'
  end
end

[].hithere # => hi

But I would recommend to define concrete sum method (starts with lower case letter, according to Ruby methods naming guidelines) instead of adding this logic to method_missing:

module Enumerable
  def sum
    # your implementation
  end
end

[].sum