select(*fields, &block)
Instance Public methods
Works in two ways.
First: Specify a subset of fields to be selected from the result set.
class Person < ActiveRecord::Base has_many :pets end person.pets # => [ # #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>, # #<Pet id: 2, name: "Spook", person_id: 1>, # #<Pet id: 3, name: "Choo-Choo", person_id: 1> # ] person.pets.select(:name) # => [ # #<Pet id: nil, name: "Fancy-Fancy">, # #<Pet id: nil, name: "Spook">, # #<Pet id: nil, name: "Choo-Choo"> # ] person.pets.select(:id, :name ) # => [ # #<Pet id: 1, name: "Fancy-Fancy">, # #<Pet id: 2, name: "Spook">, # #<Pet id: 3, name: "Choo-Choo"> # ]
Be careful because this also means you're initializing a model object
with only the fields that you've selected. If you attempt to access a
field except id that is not in the initialized record
you'll receive:
person.pets.select(:name).first.person_id # => ActiveModel::MissingAttributeError: missing attribute: person_id
Second: You can pass a block so it can be used just like Array#select. This builds an array of objects from the database for the scope, converting them into an array and iterating through them using Array#select.
person.pets.select { |pet| pet.name =~ /oo/ }
# => [
# #<Pet id: 2, name: "Spook", person_id: 1>,
# #<Pet id: 3, name: "Choo-Choo", person_id: 1>
# ]
person.pets.select(:name) { |pet| pet.name =~ /oo/ }
# => [
# #<Pet id: 2, name: "Spook">,
# #<Pet id: 3, name: "Choo-Choo">
# ]
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