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# frozen-string-literal: true
module Sequel
module Plugins
# The instance_specific_default plugin exists to make it easier to use a
# global :instance_specific association option, or to warn or raise when Sequel
# has to guess which value to use :instance_specific option (Sequel defaults to
# guessing true as that is the conservative setting). It is helpful to
# use this plugin, particularly with the :warn or :raise settings, to determine
# which associations should have :instance_specific set. Setting the
# :instance_specific to false for associations that are not instance specific
# can improve performance.
#
# Associations are instance-specific if their block calls
# a model instance method, or where the value of the block varies
# based on runtime state, and the variance is outside of a delayed evaluation.
# For example, with the following three associations:
#
# Album.one_to_one :first_track, class: :Track do |ds|
# ds.where(number: 1)
# end
#
# Album.one_to_one :last_track, class: :Track do |ds|
# ds.where(number: num_tracks)
# end
#
# Album.one_to_many :recent_tracks, class: :Track do |ds|
# ds.where{date_updated > Date.today - 10}
# end
#
# +first_track+ is not instance specific, but +last_track+ and +recent_tracks+ are.
# +last_track+ is because the +num_tracks+ call in the block is calling
# <tt>Album#num_tracks</tt>. +recent_tracks+ is because the value will change over
# time. This plugin allows you to find these cases, and set the :instance_specific
# option appropriately for them:
#
# Album.one_to_one :first_track, class: :Track, instance_specific: false do |ds|
# ds.where(number: 1)
# end
#
# Album.one_to_one :last_track, class: :Track, instance_specific: true do |ds|
# ds.where(number: num_tracks)
# end
#
# Album.one_to_many :recent_tracks, class: :Track, instance_specific: true do |ds|
# ds.where{date_updated > Date.today - 10}
# end
#
# For the +recent_tracks+ association, instead of marking it instance_specific, you
# could also use a delayed evaluation, since it doesn't actually contain
# instance-specific code:
#
# Album.one_to_many :recent_tracks, class: :Track, instance_specific: false do |ds|
# ds.where{date_updated > Sequel.delay{Date.today - 10}}
# end
#
# Possible arguments to provide when loading the plugin:
#
# true :: Set the :instance_specific option to true
# false :: Set the :instance_specific option to false
# :default :: Call super to set the :instance_specific option
# :warn :: Emit a warning before calling super to set the :instance_specific option
# :raise :: Raise a Sequel::Error if an :instance_specific option is not provided and
# an association could be instance-specific.
#
# Note that this plugin only affects associations which could be instance
# specific (those with blocks), where the :instance_specific option was not
# specified when the association was created.
#
# Usage:
#
# # Set how to handle associations that could be instance specific
# # but did not specify an :instance_specific option, for all subclasses
# # (set before creating subclasses).
# Sequel::Model.plugin :instance_specific_default, :warn
#
# # Set how to handle associations that could be instance specific
# # but did not specify an :instance_specific option, for the Album class
# Album.plugin :instance_specific_default, :warn
module InstanceSpecificDefault
# Set how to handle associations that could be instance specific but did
# not specify an :instance_specific value.
def self.configure(model, default)
model.instance_variable_set(:@instance_specific_default, default)
end
module ClassMethods
Plugins.inherited_instance_variables(self, :@instance_specific_default=>nil)
private
# Return the appropriate :instance_specific value, or warn or raise if
# configured.
def _association_instance_specific_default(name)
case @instance_specific_default
when true, false
return @instance_specific_default
when :default
# nothing
when :warn
warn("possibly instance-specific association without :instance_specific option (class: #{self}, association: #{name})", :uplevel => 3)
when :raise
raise Sequel::Error, "possibly instance-specific association without :instance_specific option (class: #{self}, association: #{name})"
else
raise Sequel::Error, "invalid value passed to instance_specific_default plugin: #{@instance_specific_default.inspect}"
end
super
end
end
end
end
end
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