This is just a question about best practices.

Imagine you have a method that takes one parameter. This parameter is the id of an object. Ideally, I would like to be able to pass either the object's id directly, or just the object itself.

What is the most elegant way to do this?

I came up with the following:

def method_name object
  object_id = object.to_param.to_i
  ### do whatever needs to be done with that object_id
end

So, if the parameter already is an id, it just pretty much stays the same; if it's an object, it gets its id.

This works, but I feel like this could be better. Also, to_param returns a string, which could in some cases return a "real" string (i.e. "string" instead of "2"), hence returning 0 upon calling to_i on it. This could happen, for example, when using the friendly id gem for classes.

Active record offers the same functionality. It doesn't matter if you say:

Table.where(user_id: User.first.id) # pass in id

or

Table.where(user_id: User.first) # pass in object and infer id

How do they do it? What is the best approach to achieve this effect?