Ruby in Sinatra using DataMapper not retrieving associations

Question

For some reason my model does not contain the associated models I linked using has n.

My definition is as follows:

class Post
    include DataMapper::Resource

    has n, :comments

    property :id, Serial
    property :name, String
end

class Comment
    include DataMapper::Resource

    belongs_to :post

    property :id, Serial
    property :comment, Text  
end

Then using the following route/code for some reason it throws an error because comments does not appear to be an attribute of user.

class MyApp < Sinatra::Application
  get "/" do

    @post = Post.get(1)    
    @post.comments.inspect
  end
end

The tables DataMapper generate seem fine (using DataMapper.finalize & DataMapper.auto_upgrade!). It has a user table and a comment table that has a foreign key on posts.id.

Any advice on this?

score 0 · Answer 1 · answered Dec 14 '11 at 13:08

0

What version of datamapper are you using?

You can create comments, save it and see what values is it storing in post_id?

Try to explicitly put the parent-key child-key relationship like this

belongs_to :post, :parent_key => [:id], :child_key => [:post_id]
property   :post_id, Integer

answered Dec 14 '11 at 13:08

ksinkar

281
2
9

1.2. when i create a comment the post_id is required so I have to fill it in when creating the comment. Also when i change my comment model to what you suggest, it doesn't work. – tomvo Dec 14 '11 at 13:31
make property time as explicitly DateTime and see what happens – ksinkar Feb 09 '12 at 17:18

score 0 · Accepted Answer · answered Dec 15 '11 at 08:53

Ok, it turns out i added a Time field to the comment declaration, like so:

class Comment
    include DataMapper::Resource

    belongs_to :post

    property :id, Serial
    property :time, Time
    property :comment, Text  
end

I'm also using MySQL which doesn't have the Time type and saves it as DateTime. When trying to retrieve the comments using Post.comments DataMapper tries to parse it as Time and dies.

Hope this saves somebody some headaches.

Ruby in Sinatra using DataMapper not retrieving associations

2 Answers2