rails 3.2 Scope with Optional Parameter

Question

I have the following scope for finding a product that belongs to a specific client.

scope :client, lambda {|client| where("client_id = ?", client) }

and can be called by

Product.client(parameter)

Is there any way I can declare my scope to return all products if a client id is not given? Is this a situation where a scope shouldn't be used?

Answer 1

It can work OK with scopes

scope :client, lambda {|client =  nil| where("client_id = ?", client) unless client.nil? }

Answer 2

You should use something other than a scope, since you really want to switch between the two cases (with/without a client id specified) and respond differently. How about this:

class Product < ActiveRecord::Base
  def self.by_client(client)
    if client
      where(client_id: client)
    else
      all
    end
  end
end

This code will always return something like the output of scope, so you can chain with it etc.

Note that this also tidies up the code and doesn't require a particular scope. And make sure you don't actually mean to have has_many :clients for the Product anyway...