Getting enum values from compiled protobuffer message in Ruby

Question

I have a compiled Ruby protobuf message like this:

  require 'google/protobuf'

  Google::Protobuf::DescriptorPool.generated_pool.build do
    add_message "PingPacket" do
      optional :message_counter, :int32, 1
      optional :message_type, :enum, 2, "PingPacket.MessageType"
    end
    add_enum "PingPacket.MessageType" do
      value :REPORT, 0
      value :LOW_BATTERY, 1
      value :LOCATE_REQUEST, 2
      value :CHECK_IN, 3
      value :SOS, 4
      value :RESTING, 5
      value :MOVING, 6
      value :EVENT, 7
      value :SYSTEM_TEST, 8
    end
  end

  PingPacket = Google::Protobuf::DescriptorPool.generated_pool.lookup("PingPacket").msgclass
  PingPacket::MessageType = Google::Protobuf::DescriptorPool.generated_pool.lookup("PingPacket.MessageType").enummodule

and Im trying to get an array with all the MessageType values. I've tried the obvious:

PingPacket::MessageType.enums
PingPacket::MessageType.values
PingPacket::MessageType.to_s

But nothing works. How can I get those values?

Answer 1

I like to inspect things with Pry, if I load the code in the pry console I get:

1) Your class is a Module

[2] pry(main)> PingPacket::MessageType.class
=> Module

If I go inside the class I get:

[4] pry(main)> cd PingPacket::MessageType
[5] pry(PingPacket::MessageType):1> ls
constants: 
  CHECK_IN  LOCATE_REQUEST  MOVING  RESTING  SYSTEM_TEST
  EVENT     LOW_BATTERY     REPORT  SOS    
PingPacket::MessageType.methods: descriptor  lookup  resolve
locals: _  __  _dir_  _ex_  _file_  _in_  _out_  _pry_

Then I can inspect all the constants:

[6] pry(PingPacket::MessageType):1> constants
=> [:CHECK_IN,
 :SOS,
 :RESTING,
 :MOVING,
 :EVENT,
 :SYSTEM_TEST,
 :REPORT,
 :LOW_BATTERY,
 :LOCATE_REQUEST]

Finally I can get, the constants value form a module with this trick:

[9] pry(PingPacket::MessageType):1> constants(false).map &method(:const_get)
=> [3, 4, 5, 6, 7, 8, 0, 1, 2]

So this will do the trick

[12] pry(main)> PingPacket::MessageType.constants(false).map &PingPacket::MessageType.method(:const_get)
=> [3, 4, 5, 6, 7, 8, 0, 1, 2]

also ypu can see that has three methods, that work as follow:

[31] pry(PingPacket::MessageType):1> resolve :CHECK_IN
=> 3
[33] pry(PingPacket::MessageType):1> lookup 3
=> :CHECK_IN
[37] pry(PingPacket::MessageType):1> descriptor.each do |i|
[37] pry(PingPacket::MessageType):1* puts i
[37] pry(PingPacket::MessageType):1* end
LOCATE_REQUEST
SOS
SYSTEM_TEST
LOW_BATTERY
EVENT
CHECK_IN
RESTING
MOVING
REPORT
=> nil

check for example this:

[42] pry(PingPacket::MessageType):1> descriptor.each do |i|
[42] pry(PingPacket::MessageType):1* puts resolve i
[42] pry(PingPacket::MessageType):1* end
2
4
8
1
7
3
5
6
0
=> nil

finally conbining all together let's put all the keys a values in a hash

[54] pry(main)> Hash[PingPacket::MessageType.descriptor.collect do |i| [i, PingPacket::MessageType.resolve(i)] end]
=> {:LOCATE_REQUEST=>2,
 :SOS=>4,
 :SYSTEM_TEST=>8,
 :LOW_BATTERY=>1,
 :EVENT=>7,
 :CHECK_IN=>3,
 :RESTING=>5,
 :MOVING=>6,
 :REPORT=>0}