Error in lib/fb_graph/post.rb regarding message_tags. "undefined method `each' for nil:NilClass"

[arronmabrey]

Seems like Facebook is sending new data that fb_graph is unable to handle.

---

The following code...

identifier = '5xxxxxxxx_xxxxxxxx8'
access_token = 'CAAE...xxx...4gtEZD'

FbGraph::Post.new(identifier, access_token: access_token).fetch

...causes this code in lib/fb_graph/post.rb#L44-L50...

44 |  if (message_tags = attributes[:message_tags])
45 |    message_tags.each do |index, message_tag|
46 |      message_tag.each do |_message_tag_|
47 |        @message_tags << TaggedObject.new(_message_tag_[:id], _message_tag_)
48 |      end
49 |    end
50 |  end

...to raise this error.

NoMethodError: undefined method `each' for nil:NilClass
from /shared/bundle/gems/fb_graph-2.7.17/lib/fb_graph/post.rb:46:in `block in initialize'

Adding debug:

44 |  if (message_tags = attributes[:message_tags])
 * |    puts "message_tags:\n\t#{message_tags.inspect}"
45 |    message_tags.each do |index, message_tag|
 * |      puts "index:\n\t#{index.inspect}"
 * |      puts "message_tag:\n\t#{message_tag.inspect}"
46 |      message_tag.each do |_message_tag_|
47 |        @message_tags << TaggedObject.new(_message_tag_[:id], _message_tag_)
48 |      end
49 |    end
50 |  end

Outputs:

message_tags:
    [{"id"=>"5xxxxx2", "name"=>"John Smith", "type"=>"user", "offset"=>0, "length"=>14}]
index:
    {"id"=>"5xxxxx2", "name"=>"John Smith", "type"=>"user", "offset"=>0, "length"=>14}
message_tag:
    nil

NoMethodError: undefined method `each' for nil:NilClass
from /shared/bundle/gems/fb_graph-2.7.17/lib/fb_graph/post.rb:49:in `block in initialize'

---

Let me know if you need additional information. I'm happy to help.

Thanks, -- Arron

EDIT: we're using the latest version fb_graph-2.7.17

[nov]

Hum, FB returned wrong format of message tags. There are no changes in message tags format during v1.0 to v2.2. https://developers.facebook.com/docs/graph-api/reference/v2.2/post

Probably asking to FB developer support is better.

[arronmabrey]

The FB docs seem to suggest the data that was received is correct. Unless I'm missing something, which happens most of the time :smile:

data received

[
  { 
    "id" => "5xxxxx2",
    "name" => "John Smith",
    "type" => "user",
    "offset" => 0,
    "length" => 14
  }
]

Here is a pull-request that works correctly with the data FB is sending. https://github.com/nov/fb_graph/pull/382

[nov]

No, message_tags on posts should be a JSON object (Hash in ruby), not JSON array. ref.) https://github.com/nov/fb_graph-mock/blob/master/mock_json/posts/with_message.json

You might be fetching another type of object. Try fetch the object using Graph API Explorer with "metadata=true" option, then you'll see "type". https://developers.facebook.com/tools/explorer

[arronmabrey]

@nov thanks for the "metadata=true" tip. It looks like the object is a "comment" not a post. Sorry for the trouble. :-)