CODEWITHSUNDEEP
rubymongodbmongomapper
Mandar Pathak
Mandar Pathak

Reputation: 870

MongoMapper belongs_to relation returns nil

I have the following MongoMapper models:

class Album
  include MongoMapper::Document
  key :name, String
  timestamps!

  many :photos
end


class Photo
  include MongoMapper::Document
  key :caption, String
  timestamps!

  key :album_id, ObjectId
  belongs_to :album
end

I am creating instances of the album and photo object as follows:

album = Album.create!(name: "NYE 2013")
photo = Photo.create!(caption: "Happy New Year!", album: album)

After this, when I execute photo.album == album it returns true as long as I haven't reloaded the photo object. However, as soon as I reload the photo object from the database by doing either photo.reload or at a later time, photo.album returns nil.

At all times, album.photos does include the said photo object, which is confusing me.

Is there something I am missing or doing wrong? As usual, thanks for all the help!

Upvotes: 1

Views: 118

Answers (1)

Jon Kern
Jon Kern

Reputation: 3235

Make sure you have your environment set up right and the proper gems loaded...

I am currently using 

gem 'mongo_mapper', :git => "git://github.com/mongomapper/mongomapper.git", :tag => "v0.13.0.beta2"

So I fired up mmconsole and added your class defs above, and then executed your two document creation lines. Literally cut-n-paste it in... It all worked as expected:

2.0.0-p247 :016 > album = Album.create!(name: "NYE 2013")
 => #<Album _id: BSON::ObjectId('5321213766e76cf398000001'), created_at: 2014-03-13 03:08:39 UTC, name: "NYE 2013", updated_at: 2014-03-13 03:08:39 UTC> 
2.0.0-p247 :017 > Album.count
 => 1 
2.0.0-p247 :018 > photo = Photo.create!(caption: "Happy New Year!", album: album)
 => #<Photo _id: BSON::ObjectId('5321214966e76cf398000002'), album_id: BSON::ObjectId('5321213766e76cf398000001'), caption: "Happy New Year!", created_at: 2014-03-13 03:08:57 UTC, updated_at: 2014-03-13 03:08:57 UTC> 
2.0.0-p247 :019 > Photo.count
 => 1 
2.0.0-p247 :020 > photo.album.name
 => "NYE 2013" 
2.0.0-p247 :021 > photo.inspect
 => "#<Photo _id: BSON::ObjectId('5321214966e76cf398000002'), album_id: BSON::ObjectId('5321213766e76cf398000001'), caption: \"Happy New Year!\", created_at: 2014-03-13 03:08:57 UTC, updated_at: 2014-03-13 03:08:57 UTC>" 
2.0.0-p247 :022 > foto=Photo.first
 => #<Photo _id: BSON::ObjectId('5321214966e76cf398000002'), album_id: BSON::ObjectId('5321213766e76cf398000001'), caption: "Happy New Year!", created_at: 2014-03-13 03:08:57 UTC, updated_at: 2014-03-13 03:08:57 UTC> 
2.0.0-p247 :023 > foto.album.name
 => "NYE 2013"

This should help you debug...

This older github mongo_examples project shows a handful of ways to implement associations.

Upvotes: 1

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