Class: Pbbuilder

Inherits:
BasicObject
Defined in:
lib/pbbuilder.rb,
lib/pbbuilder/railtie.rb

Overview

Pbbuilder makes it easy to create a protobuf message using the builder pattern It is heavily inspired by jbuilder

Given this example message definition: message Person 

string name = 1;
repeated Person friends = 2;

You could use Pbbuilder as follows: person = RPC::Person.new Pbbuilder.new(person) do |pb|

pb.name "Hello"
pb.friends [1, 2, 3] do |number|
  pb.name "Friend ##{number}"
end

end

message.name => “Hello”

It basically works exactly like jbuilder. The main difference is that it can use introspection to figure out what kind of protobuf message it needs to create.

Defined Under Namespace

Classes: Railtie

Instance Method Summary collapse

Constructor Details

#initialize(message) {|_self| ... } ⇒ Pbbuilder

Returns a new instance of Pbbuilder.

Yields:

  • (_self)

Yield Parameters:

  • _self (Pbbuilder) —

    the object that the method was called on



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# File 'lib/pbbuilder.rb', line 25

def initialize(message)
  @message = message

  yield self if ::Kernel.block_given?
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(field, *args, &block) ⇒ Object 



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# File 'lib/pbbuilder.rb', line 31

def method_missing(field, *args, &block)
  set!(field, *args, &block)
end

Instance Method Details

#extract!(element, *args) ⇒ Object 



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# File 'lib/pbbuilder.rb', line 78

def extract!(element, *args)
  args.each do |arg|
    value = element.send(arg)
    @message[arg.to_s] = value
  end
end

#respond_to_missing?(field) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pbbuilder.rb', line 35

def respond_to_missing?(field)
  !!@message.class.descriptor.lookup(field.to_s)
end

#set!(field, *args, &block) ⇒ Object 



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# File 'lib/pbbuilder.rb', line 39

def set!(field, *args, &block)
  name = field.to_s
  descriptor = @message.class.descriptor.lookup(name)

  if block
    raise ::ArgumentError, "can't pass block to non-message field" unless descriptor.type == :message

    if descriptor.label == :repeated
      # pb.field @array { |element| pb.name = element.name }
      raise ::ArgumentError, "wrong number of arguments (expected 1)" unless args.length == 1
      collection = args.first
      _append_repeated(name, descriptor, collection, &block)
      return
    end

    raise ::ArgumentError, "wrong number of arguments (expected 0)" unless args.empty?
    # pb.field { pb.name = "hello" }
    message = (@message[name] ||= _new_message_from_descriptor(descriptor))
    _scope(message, &block)
  elsif args.length == 1
    @message[name] = args.first
  else
    # pb.field @value, :id, :name, :url
    element = args.shift
    if descriptor.label == :repeated
      # If the message field that's being assigned is a repeated field, then we assume that `element` is enumerable.
      # This way you can do something like pb.repeated_field @array, :id, :name
      # This will create a message out of every object in @array, copying over the :id and :name values.
      set!(name, element) do |item|
        extract!(item, *args)
      end
    else
      set!(name) do
        extract!(element, *args)
      end
    end
  end
end

#target! ⇒ Object 



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# File 'lib/pbbuilder.rb', line 85

def target!
  @message
end