Question

I want to make a generic method that will take either a single object or collection, and then return an array of id’s, and the actual id to take from the object/collection will also be passed in as a parameter.

Example:

a = []
a << get_ids("car_id", some_object)
a << get_ids("user_id", some_collection)


def self.get_ids(id_name, obj)
  # ??
end

This needs metaprogramming I know, but how do I figure out if its a collection or not?
do I send a message to check if “id_name” is a property?

Also, I currently need this type of functionality, so I thought of making it generic so I can re-use it. Does it have any major performance implications?

Answer 1

def self.get_ids(id_name, obj)
  if obj.is_a? Enumerable
    obj.collect {|e| e.send(id_name) }
  else
    obj.send(id_name)
  end
end

Alternatively,

def self.get_ids(id_name, *objs)
  objs.collect {|e| e.send(id_name) }
end
...
a << get_ids("car_id", some_object)
a << get_ids("user_id", *some_collection)