CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-3
omarArroum
omarArroum

Reputation: 255

Updating/Saving an attribute in a join model

I have a join model called AppServer which references three other models called Environment, Server and App. I also added another field in the AppServer model called app_server_id, as I set id => false for the AppServer model. I added the app_server_id field at a later stage, after having populated the table and not getting any further with my other question.

So since I now have app_server_id, I tried to populate it, using the following method in the AppServer model:

def generate_id
  "#{environment_id}_#{app_id}_#{server_id}"
end

however, in the rails console I wanted to see whether the method works so I done this:

pry(main)> AppServer.first.generate_id
=> "2_3_1"

So now trying either to update the attribute or save it won't work as shown:

pry(main)> AppServer.first.app_server_id = AppServer.first.generate_id
=> "2_3_1"
pry(main)> AppServer.first.app_server_id
=> nil

or

pry(main)> AppServer.first.update_attribute(:app_server_id, AppServer.first.generate_id)
NoMethodError: undefined method `eq' for nil:NilClass
from C:/Ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/active_support/whiny_nil.rb:48:in `method_missing'

or even

pry(main)> apps=AppServer.first
=> #<AppServer app_id: 3, server_id: 1, environment_id: 2, app_server_id: nil>
pry(main)> apps.app_server_id = apps.generate_id
=> "2_3_1"
pry(main)> apps.save
NoMethodError: undefined method `eq' for nil:NilClass
from C:/Ruby192/lib/ruby/gems/1.9.1/gems/activesupport-3.0.9/lib/active_support/whiny_nil.rb:48:in `method_missing'

Any idea why that could be?

If you guys need any more code let me know

Upvotes: 1

Views: 205

Answers (1)

mark
mark

Reputation: 10564

This

pry(main)> AppServer.first.app_server_id = AppServer.first.generate_id
=> "2_3_1"
pry(main)> AppServer.first.app_server_id
=> nil

doesn't work because you're assigning the app_server_id, not saving it, then referencing the saved version (nil) again.

For this

undefined method `eq' for nil:NilClass

see this question

undefined method `eq' for nil:NilClass with rails 3 and ruby enterprise on ubuntu hardy

Edit

I see no benefit not to auto increment this so I would add an id column using this migration and remove your to_param method:

def self.up
  execute "ALTER TABLE 'app_servers'
              ADD COLUMN 'id' INT(11) AUTO_INCREMENT NOT NULL FIRST,
              ADD PRIMARY KEY('id')"
end

Credit where due

Upvotes: 1

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