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| [RW] | bind_values | |
| [RW] | create_with_value | |
| [RW] | eager_load_values | |
| [RW] | from_value | |
| [RW] | group_values | |
| [RW] | having_values | |
| [RW] | includes_values | |
| [RW] | joins_values | |
| [RW] | limit_value | |
| [RW] | lock_value | |
| [RW] | offset_value | |
| [RW] | order_values | |
| [RW] | preload_values | |
| [RW] | readonly_value | |
| [RW] | reordering_value | |
| [RW] | reverse_order_value | |
| [RW] | select_values | |
| [RW] | uniq_value | |
| [RW] | where_values |
# File activerecord/lib/active_record/relation/query_methods.rb, line 263 def build_arel arel = table.from table build_joins(arel, @joins_values) unless @joins_values.empty? collapse_wheres(arel, (@where_values - ['']).uniq) arel.having(*@having_values.uniq.reject{|h| h.blank?}) unless @having_values.empty? arel.take(connection.sanitize_limit(@limit_value)) if @limit_value arel.skip(@offset_value.to_i) if @offset_value arel.group(*@group_values.uniq.reject{|g| g.blank?}) unless @group_values.empty? order = @order_values order = reverse_sql_order(order) if @reverse_order_value arel.order(*order.uniq.reject{|o| o.blank?}) unless order.empty? build_select(arel, @select_values.uniq) arel.distinct(@uniq_value) arel.from(@from_value) if @from_value arel.lock(@lock_value) if @lock_value arel end
Used to extend a scope with additional methods, either through a module or through a block provided.
The object returned is a relation, which can be further extended.
Using a module
module Pagination def page(number) # pagination code goes here end end scope = Model.scoped.extending(Pagination) scope.page(params[:page])
You can also pass a list of modules:
scope = Model.scoped.extending(Pagination, SomethingElse)
Using a block
scope = Model.scoped.extending do def page(number) # pagination code goes here end end scope.page(params[:page])
You can also use a block and a module list:
scope = Model.scoped.extending(Pagination) do def per_page(number) # pagination code goes here end end
Replaces any existing order defined on the relation with the specified order.
User.order('email DESC').reorder('id ASC') # generated SQL has 'ORDER BY id ASC'
Subsequent calls to order on the same relation will be appended. For example:
User.order('email DESC').reorder('id ASC').order('name ASC')
generates a query with ‘ORDER BY id ASC, name ASC’.
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
Specifies whether the records should be unique or not. For example:
User.select(:name) # => Might return two records with the same name User.select(:name).uniq # => Returns 1 record per unique name User.select(:name).uniq.uniq(false) # => You can also remove the uniqueness