class ActiveRecord::Precounter

Constants

VERSION

Public Class Methods

new(relation) click to toggle source

@param [ActiveRecord::Relation] relation - Parent resources relation.

# File lib/active_record/precounter.rb, line 9
def initialize(relation)
  @relation = relation
end

Public Instance Methods

precount(*association_names) click to toggle source

@param [Array<String,Symbol>] association_names - Eager loaded association names. e.g. `[:users, :likes]` @return [Array<ActiveRecord::Base>]

# File lib/active_record/precounter.rb, line 15
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 Instance Methods

define_count_accessor(klass, association_name) click to toggle source

@param [Class] record class @param [String] association_name @return [String] writer method name

# File lib/active_record/precounter.rb, line 64
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