Single Ruby/Rails method to check an object both exists and has an ID

Question

Before I start littering my code with an unwieldy method of my own creation, I'm wondering if there's an existing Ruby/Rails method that will:

• Returns true if @foo exists and @foo has an ID (e.g. you're in the foo#show)
• Returns false if @foo exists but does not yet have an ID (e.g. you're in foo#new)
• Returns false if @foo does not exist (e.g. you're in bar#index)

I've tried to search the API docs but the terms I'm using are by necessity so general (ID, save, exists, etc) that I've not found anything so far.

Answer 1

For first 2, use !@foo.new_record? new_record? method returns true/false if model was saved to database and have id or not.

For third, read this: defined?

Answer 2

You can use .try

@foo.try(:id)

will return id or nil.

If you strictly want true or false,

!!@foo.try(:id)