Rails.where vs .find

Question

I noticed that the Model.where method always returns an array, even if there is only one result when the Model.find method Model.find not work. Is there a reason for this? I thought Model.where was the preferred feature since Rails 3.X.

Should I use Model.find when I expect one result and Model.where when I expect more than one result?

Answer 1

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

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

  While find can return an array of records, rather than a link - if a list of identifiers is given, using where is preferred with Rails 3. Many similar uses of find now deprecated or gone completely .

So yes, if you only want and expect a single object, it is easier to use find , since otherwise you have to call Model.where.first .

Note that the old-style hash parameters for find and many of the dynamic find_ methods find_ deprecated as Rails 4.0 ( see the corresponding release notes ).

Answer 2

In fact, find_by gets the model object from where obtained by ActiveRecord::Relation

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

Source

Answer 3

Model.find uses the primary key column. Therefore, there is always exactly one or no result. Use it when you are looking for one specific item identified by an identifier.