CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-2
martincarlin87
martincarlin87

Reputation: 11042

Can't access foreign key property in Rails

I have two classes - pop_vlans and logical_interfaces defined as follows:

logical_interface.rb

class LogicalInterface < ActiveRecord::Base
  has_many :pop_vlans
end

pop_vlans.rb

class PopVlan < ActiveRecord::Base
  self.table_name = 'pop_vlans'
  belongs_to :logical_interface, :class_name => "LogicalInterface", :foreign_key => "vlan_id"
end

Then in my controller I am trying to access the pop_id column of the related pop_vlans object but I get an undefined error:

logical_interface_controller.rb

def update
  if params[:id]
    @logical_interface = LogicalInterface.find(params[:id]) 

     @pop_id = @logical_interface.pop_vlan.pop_id # error
  end
end

However, I can get the property I want but it requires a few extra lines:

@vlan_id = @logical_interface.vlan_id

@pop_vlan = PopVlan.find(@vlan_id) 

@pop_id = @pop_vlan.pop_id

but I'd rather make my scripts a bit more concise (plus, find out why the above doesn't work aswell as it's genuinely annoying me!).

Upvotes: 0

Views: 71

Answers (1)

Pierre-Louis Gottfrois
Pierre-Louis Gottfrois

Reputation: 17631

You have define

has_many :pop_vlans

which means you must access it with

@logical_interface = LogicalInterface.find(...)
@logical_interface.pop_vlans # return an array of pop_vlans
#                          ^

@logical_interface.pop_vlans.map(&:pop_id) # return an array of pop_ids

Upvotes: 1

Related Questions