Module: Shamu::Services::LazyAssociation

Defined in:
lib/shamu/services/lazy_association.rb

Overview

Lazily look up an associated resource

Constant Summary collapse

EXCLUDE_PATTERN =

rubocop:disable Metrics/LineLength

/\A(block_given\?|id|send|public_send|iterator|object_id|to_model_id|binding|class|kind_of\?|is_a\?|instance_of\?|respond_to\?|p.+_methods|__.+__)\z/
MUTEX = 
Mutex.new

Class Method Summary collapse

Class Method Details

.class_for(klass) ⇒ Object

rubocop:disable Metrics/MethodLength, Metrics/PerceivedComplexity



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# File 'lib/shamu/services/lazy_association.rb', line 9

def self.class_for( klass ) # rubocop:disable Metrics/MethodLength, Metrics/PerceivedComplexity
  return klass.const_get( :Lazy_ ) if klass.const_defined?( :Lazy_ )

  MUTEX.synchronize do

    # Check again in case another thread defined it while waiting for the
    # mutex
    return klass.const_get( :Lazy_ ) if klass.const_defined?( :Lazy_ )

    lazy_class = Class.new( klass ) do
      # Remove all existing public methods so that they can be delegated
      # with #method_missing.
      klass.public_instance_methods.each do |method|
        next if EXCLUDE_PATTERN =~ method
        undef_method method
      end

      def initialize( id, &block )
        @id = id
        @block = block
      end

      # @!attribute
      # @return [Object] the primary key id of the association. Not delegated so
      #     it is safe to use and will not trigger an unnecessary fetch.
      attr_reader :id

      def __getobj__
        return @association if defined? @association

        @association = @block.call( @id ) if @block
      end

      def method_missing( method, *args, &block )
        if respond_to_missing?( method )
          __getobj__.public_send( method, *args, &block )
        else
          super
        end
      end

      def respond_to_missing?( method, include_private = false )
        __getobj__.respond_to?( method, include_private ) || super
      end

    end

    klass.const_set( :Lazy_, lazy_class )
    lazy_class
  end
end