How to get specific field of a many-to-many related document?

[mari...@gmail.com]

Hi,

I'm trying to figure out how exactly I could get a specific field of a many-to-many related document.
Here's a link to my SO question: http://stackoverflow.com/q/15787618/1313143

I have a model called ChildTemplate that has this key:

  key :used_parameters, Array
  many :parameters, :in => :used_parameters

I need only the ID field of the associated parameters. I've tried a number of ways:

used_parameters.name
used_parameters[:name]
parameters.name
parameters[:name]
Parameter.find(used_parameters)[:name]

This is done from within a validation function in the model. All of the above fails. What is the proper way?

[Jamie Orchard-Hays]

See if this helps:

http://mongomapper.com/documentation/plugins/associations.html

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[mari...@gmail.com]

Not really, sorry.. Of course I've read the documentation, but in there I can't find what I'm looking for.

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[Jamie Orchard-Hays]

ct = ChildTemplate.find(<id>)

ct.parameters #=> lazy loads the parameters

ct.parameters.build(:your => value, ...) #=> builds new parameter, but doesn't save

ct.parameters.create(same as above) #=> builds, saves new parameter

ct.parameters << Parameter.new(...) #=> appends, saves new parameter

ct.parameters.first.name #=> name attr of the first parameter

You can create finder methods on your association and there are some built-in.

Have a look in the tests for many more examples:

https://github.com/jnunemaker/mongomapper/tree/master/test