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require 'active_record/precounter/version'
require 'active_record/precountable'
module ActiveRecord
class Precounter
class MissingInverseOf < StandardError; end
# @param [ActiveRecord::Relation] relation - Parent resources relation.
def initialize(relation)
@relation = relation
end
# @param [Array<String,Symbol>] association_names - Eager loaded association names. e.g. `[:users, :likes]`
# @return [Array<ActiveRecord::Base>]
def precount(*association_names)
# Allow single record instances as well as relations to be passed.
# The splat here will return an array of the single record if it's
# not a relation or otherwise return the records themselves via #to_a.
records = *@relation
return records if records.empty?
# We need to get the relation's active class, which is the class itself
# in the case of a single record.
klass = @relation.respond_to?(:klass) ? @relation.klass : @relation.class
association_names.each do |association_name|
association_name = association_name.to_s
reflection = klass.reflections.fetch(association_name)
if reflection.inverse_of.nil?
raise MissingInverseOf.new(
"`#{reflection.klass}` does not have inverse of `#{klass}##{reflection.name}`. "\
"Probably missing to call `#{reflection.klass}.belongs_to #{klass.name.underscore.to_sym.inspect}`?"
)
end
primary_key = reflection.inverse_of.association_primary_key.to_sym
count_by_id = if reflection.has_scope?
# ActiveRecord 5.0 unscopes #scope_for argument, so adding #where outside that:
# https://github.com/rails/rails/blob/v5.0.7/activerecord/lib/active_record/reflection.rb#L314-L316
reflection.scope_for(reflection.klass.unscoped).where(reflection.inverse_of.name => records.map(&primary_key)).group(
reflection.inverse_of.foreign_key
).count
else
reflection.klass.where(reflection.inverse_of.name => records.map(&primary_key)).group(
reflection.inverse_of.foreign_key
).count
end
writer = define_count_accessor(klass, association_name)
records.each do |record|
record.public_send(writer, count_by_id.fetch(record.public_send(primary_key), 0))
end
end
records
end
private
# @param [Class] record class
# @param [String] association_name
# @return [String] writer method name
def define_count_accessor(klass, association_name)
reader_name = "#{association_name}_count"
writer_name = "#{reader_name}="
if !klass.method_defined?(reader_name) && !klass.method_defined?(writer_name)
klass.extend(ActiveRecord::Precountable)
klass.public_send(:precounts, association_name)
end
writer_name
end
end
end
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