Minecart Injectable

injectable.rb

module Minecart
  module Injectable
    module ClassMethods
      # USAGE
      # @param field
      #   The name of the instance variable to set with the injected value
      # @param opts
      #   :with - a ruby java class i.e. (java.lang.String) which the config value can be cast into.
      #   :named - a string which will be used to retrieve an object annotated with the @Named convention.
      #   :annotated - a ruby java binding annotation which is used to retrieve the requested object
      def inject(field, opts = {})
        attr_reader field
        injections[field] = opts
      end
  
      def new(*args)
        res = injectable_original_new(*args)
        res.injectable_process_injections(Minecart::Injectable.injector)
        res
      end
  
      def injections
        @injections ||= {}
      end
    end
  
    def self.injector
      @injector || raise("No Injector :(")
    end
  
    def self.with_injector(injector)
      original = @injector
      @injector = injector
      yield
    ensure
      @injector = original
    end
  
    def self.set_injector(injector)
      @injector = injector
    end
  
    def self.included(base)
      base.class.__send__(:alias_method, :injectable_original_new, :new)
      base.extend ClassMethods
    end
  
    def injectable_process_injections(injector)
      self.class.injections.each do |field_name, opts|
        klass = opts[:with]
        if opts[:named]
          key = com.google.inject.Key.get(klass.java_class, com.google.inject.name.Names.named(opts[:named]))
        elsif opts[:annotated]
          key = com.google.inject.Key.get(klass.java_class, opts[:annotated].java_class)
        else
          key = klass.java_class
        end
  
        instance = injector.getInstance(key)
        instance_variable_set(:"@#{field_name}", instance)
      end
    end
  end
end