Class: Pbbuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/pbbuilder.rb,
lib/pbbuilder/errors.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.

Direct Known Subclasses

PbbuilderTemplate

Defined Under Namespace

Classes: MergeError, 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 31

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 ⇒ Object 



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# File 'lib/pbbuilder.rb', line 37

def method_missing(...)
  set!(...)
end

Instance Method Details

#extract!(element, *args) ⇒ Object 



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# File 'lib/pbbuilder.rb', line 103

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

#merge!(object) ⇒ Object

Merges object into a protobuf message, mainly used for caching.

Parameters:

  • object (Hash) 


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# File 'lib/pbbuilder.rb', line 113

def merge!(object)
  ::Kernel.raise Pbbuilder::MergeError.build(target!, object) unless object.class == ::Hash

  object.each_key do |key|
    if object[key].respond_to?(:empty?) && object[key].empty?
      ::Kernel.raise Pbbuilder::MergeError.build(target!, object)
    end

    if object[key].class == ::String
      # pb.fields {"one" => "two"}
      @message[key.to_s] = object[key]
    elsif object[key].class == ::Array
      # pb.tags ['test', 'ok']
      @message[key.to_s].replace object[key]
    elsif object[key].class == ::TrueClass || object[key].class == ::FalseClass
      # pb.boolean true || false
      @message[key.to_s] = object[key]
    elsif ( obj = object[key]).class == ::Hash
      # pb.field_name do
      #    pb.tags ["ok", "cool"]
      # end
      #

      # optional empty fields don't show up in @message object,
      # we recreate empty message, so we can fill it with values
      if @message[key.to_s].nil?
        field_descriptor = @message.class.descriptor.lookup(key.to_s)
        @message[key.to_s] = _new_message_from_descriptor(field_descriptor)
      end

      @message[key.to_s] = _scope(@message[key.to_s]) { self.merge!(obj) }
    end
  end
end

#respond_to_missing?(field) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pbbuilder.rb', line 41

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 45

def set!(field, *args, &block)
  name = field.to_s
  descriptor = @message.class.descriptor.lookup(name)
  ::Kernel.raise ::ArgumentError, "Unknown field #{name}" if descriptor.nil?

  if block
    ::Kernel.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 }
      ::Kernel.raise ::ArgumentError, "wrong number of arguments #{args.length} (expected 1)" unless args.length == 1
      collection = args.first
      _append_repeated(name, descriptor, collection, &block)
      return
    end

    ::Kernel.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
    arg = args.first
    if descriptor.label == :repeated
      if arg.respond_to?(:to_hash)
        # pb.fields {"one" => "two"}
        arg.to_hash.each do |k, v|
          @message[name][k] = v
        end
      elsif arg.respond_to?(:to_ary)
        # pb.fields ["one", "two"]
        # Using concat so it behaves the same as _append_repeated
        @message[name].concat arg.to_ary
      else
        # pb.fields "one"
        @message[name].push arg
      end
    else
      # pb.field "value"
      @message[name] = arg
    end
  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

Returns Initialized message object.

Returns:

  • Initialized message object



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# File 'lib/pbbuilder.rb', line 149

def target!
  @message
end