instance method `select`

Ruby on Rails 3.2.22.5

Since v3.0.20

Available in: v3.0.20 v3.1.12 v3.2.22.5 v4.0.13 v4.1.16 v4.2.9 v5.2.8.1 v6.0.6 v6.1.7.10 v7.0.10 v7.1.6 v7.2.3 v8.0.4 v8.1.2

Compare with:

select(value = Proc.new)

Works in two unique ways.

First: takes a block so it can be used just like Array#select.

Model.scoped.select { |m| m.field == value }

This will build an array of objects from the database for the scope, converting them into an array and iterating through them using Array#select.

Second: Modifies the SELECT statement for the query so that only certain fields are retrieved:

>> Model.select(:field)
=> [#<Model field:value>]

Although in the above example it looks as though this method returns an array, it actually returns a relation object and can have other query methods appended to it, such as the other methods in ActiveRecord::QueryMethods.

The argument to the method can also be an array of fields.

>> Model.select([:field, :other_field, :and_one_more])
=> [#<Model field: "value", other_field: "value", and_one_more: "value">]

Any attributes that do not have fields retrieved by a select will raise a ActiveModel::MissingAttributeError when the getter method for that attribute is used:

>> Model.select(:field).first.other_field
=> ActiveModel::MissingAttributeError: missing attribute: other_field

Parameters

value opt = Proc.new

Source

# File activerecord/lib/active_record/relation/query_methods.rb, line 70
    def select(value = Proc.new)
      if block_given?
        to_a.select {|*block_args| value.call(*block_args) }
      else
        relation = clone
        relation.select_values += Array.wrap(value)
        relation
      end
    end

Defined in activerecord/lib/active_record/relation/query_methods.rb line 70 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveRecord::QueryMethods

Signature

Parameters