Rails 4: find_or_initialize_by and conditional default values

Question

I've got a class that builds a relation like so:

def assign_vars
  template_variables.each do |master|
    @document.template_variables.find_or_initialize_by(
      name: master.name, tag: master.tag, text: master.default_value)
    end
  end
end

So that it will be found if it's already there or built if it's not. My problem is with the text: master.default_value . I want to set that only if we're building new relations and not for ones found with find_or_initialize_by . Something like text: text || master.default_value text: text || master.default_value . How can I write that in that loop?

Answer 1

If you study the implementation of find_or_initialize_by ,

def find_or_initialize_by(attributes, &block)
  find_by(attributes) || new(attributes, &block)
end

you will see it expects attributes as well as a block . Attributes are used for finding the record only. So you can pass a block to initialize the default attributes during instantiation of the new object.

So, to set default text value only if record not found, you might try this:

def assign_vars
  template_variables.each do |master|
    @document.template_variables.find_or_initialize_by(
      name: master.name, tag: master.tag) do |t| 
        t.text = master.default_value
      end
    end
  end
end