Can't destroy record in many-to-many relationship
- by Dmart
I'm new to Rails, so I'm sure I've made a simple mistake.
I've set up a many-to-many relationship between two models: User and Group. They're connected through the junction model GroupMember.
Here are my models (removed irrelevant stuff):
class User < ActiveRecord::Base
has_many :group_members
has_many :groups, :through => :group_members
end
class GroupMember < ActiveRecord::Base
belongs_to :group
belongs_to :user
end
class Group < ActiveRecord::Base
has_many :group_members
has_many :users, :through => :group_members
end
The table for GroupMembers contains additional information about the relationship, so I didn't use has_and_belongs_to_many (as per the Rails "Active Record Associations" guide).
The problem I'm having is that I can't destroy a GroupMember.
Here's the output from rails console:
irb(main):006:0> m = GroupMember.new
=> #<GroupMember group_id: nil, user_id: nil, active: nil, created_at: nil, updated_at: nil>
irb(main):007:0> m.group_id =1
=> 1
irb(main):008:0> m.user_id = 16
=> 16
irb(main):009:0> m.save
=> true
irb(main):010:0> m.destroy
NoMethodError: undefined method `eq' for nil:NilClass
from /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/active_support/whiny_nil.rb:48:in `method_missing'
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/persistence.rb:79:in `destroy'
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/locking/optimistic.rb:110:in `destroy'
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/callbacks.rb:260:in `destroy'
from /usr/local/lib/ruby/gems/1.8/gems/activesupport-3.0.4/lib/active_support/callbacks.rb:413:in `_run_destroy_callbacks'
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/callbacks.rb:260:in `destroy'
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/transactions.rb:235:in `destroy'
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/transactions.rb:292:in `with_transaction_returning_status'
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/connection_adapters/abstract/database_statements.rb:139:in `transaction'
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/transactions.rb:207:in `transaction'
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/transactions.rb:290:in `with_transaction_returning_status'
from /usr/local/lib/ruby/gems/1.8/gems/activerecord-3.0.4/lib/active_record/transactions.rb:235:in `destroy'
from (irb):10
This is driving me crazy, so any help would be greatly appreciated.
