CODEWITHSUNDEEP
rubydatabasedatamapper
sdawes
sdawes

Reputation: 661

DataMapper add property from another class to table of a different class.

I am new to using DataMapper and simply want to add a property from one class, to a table in another. I have two classes, as seen below: I would like to add the 'handle' property from the class 'user', as a column in the table for 'peep'. I have required all the relevant gems (not included below) but am struggling with the DataMapper syntax. I have tried variants of has n, :user and belongs to etc, but all result in a 'user_id has NULL values' errors.

Class 'user':

class User

      include DataMapper::Resource

      property :id,               Serial
      property :email,            String, format: :email_address, required: true, unique: true
      property :handle,           String, required: true
  end

Class 'peep':

class Peep

  include DataMapper::Resource

  property :id,            Serial
  property :peep_content,  String
  property :created_at,    DateTime

end

Upvotes: 0

Views: 77

Answers (1)

Larry Lv
Larry Lv

Reputation: 769

Seems duplicated with your another question:Data Mapper Associations - what code?

But here is my answer, when the association keys are not conventional id or ..._id, you have to specify it explicitly when you add the association, to let DataMapper know how to query the relation for you.

Doc: http://datamapper.org/docs/associations.html Customizing Associations section.

class User
  ...
  has n, :peeps, 'Peep',
    :parent_key => [ :handle ],      # local to this model (User)
    :child_key  => [ :user_handle ]  # in the remote model (Peep)
end

class Peep
  ...
  belongs_to :user, 'User',
    :parent_key => [ :handle ],      # in the remote model (Peep)
    :child_key  => [ :user_handle ]  # local to this model (User)
end

Upvotes: 0

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