Rails .where vs .find

Question

I've noticed that the Model.where method always returns an array even if there is only one result where as the Model.find method doesn't. Is there any reason for this? I thought Model.where was the preferred function since Rails 3.X.

Should I be using Model.find when I expect a single result and Model.where when I expect more than one result?

Answer 1

• where returns an ActiveRecord::Relation (not an array, even though it behaves much like one), which is a collection of model objects. If nothing matches the conditions, it simply returns an empty relation.

• find (and its related dynamic find_by_columnname methods) returns a single model object. If nothing is found, an ActiveRecord::RecordNotFound exception is raised (but not with the dynamic find_by_ methods).

  While find can return an Array of records—not a Relation—if given a list of IDs, using where is preferred since Rails 3. Many similar uses of find are now deprecated or gone entirely .

So yes, if you only want and expect a single object, using find is easier, as otherwise you must call Model.where.first .

Note that old-style hash options to find and many dynamic find_ methods are deprecated as of Rails 4.0 ( see relevant release notes ).

Answer 2

Actually find_by takes a model object from where obtained ActiveRecord::Relation

def find_by(*args)
  where(*args).take
end

Source

Answer 3

Model.find is using the primary key column. Therefore there is always exactly one or no result. Use it when you are looking for one specific element identified by it's id.