I'm doing this tutorial and am stuck in the Tagging part. Basically I have articles that can have a list of tags. As one article can has multiple tags and vice versa, there is an additional taggings model, through which this association is modelled. Here are the models:
class Article < ActiveRecord::Base
has_many :comments
has_many :taggings
has_many :tags, through: :taggings
end
class Tag < ActiveRecord::Base
has_many :taggings
has_many :articles, through: :taggings
end
class Tagging < ActiveRecord::Base
belongs_to :tag
belongs_to :article
end
and the migrations:
def change
create_table :articles do |t|
t.string :title
t.text :body
t.timestamps
end
create_table :tags do |t|
t.string :name
t.timestamps
end
create_table :taggings do |t|
t.references :tag, index: true
t.references :article, index: true
t.timestamps
end
There's also an article_controller with (amongst others):
def create
@article = Article.new(article_params)
@article.save
redirect_to article_path(@article)
end
Now, as the tutorial suggets, when I try to create a new tag with the rails console for an article, I get a NoMethodError for a nil:NilClass:
head :011 > Article.first.tags.create(name: "tag")
Article Load (0.5ms) SELECT "articles".* FROM "articles" ORDER BY "articles"."id" ASC LIMIT 1
(0.2ms) begin transaction
SQL (0.8ms) INSERT INTO "tags" ("created_at", "name", "updated_at") VALUES (?, ?, ?) [["created_at", ...], ["name", "tag"], ["updated_at", ...]]
SQL (2.1ms) INSERT INTO "taggings" ("article_id", "created_at", "tag_id", "updated_at") VALUES (?, ?, ?, ?) [["article_id", 1], ["created_at", ...], ["tag_id", 7], ["updated_at", ...]]
(0.6ms) rollback transaction
NoMethodError: undefined method `name' for nil:NilClass
So it seems to me, as if the tag entry is created, as well as the correct taggings entry, but apparently at some point it struggles to find the correct tag, hence the error. Am I right? How can I fix this?
I found a lot of questions on SO regarding this kind of error, but each was caused by some problem I couldn't relate to mine...
UPDATE:
reloading or restarting the rails console has no effect.
Here is the error backtrace, with path as ~/.rvm/gems/ruby-head/gems/activerecord-4.0.4/lib/active_record:
from path/associations/has_many_association.rb:81:in `cached_counter_attribute_name'
from path/associations/has_many_association.rb:77:in `has_cached_counter?'
from path/associations/has_many_association.rb:85:in `update_counter'
from path/associations/has_many_through_association.rb:66:in `insert_record'
from path/associations/collection_association.rb:463:in `block (2 levels) in create_record'
from path/associations/collection_association.rb:367:in `add_to_target'
from path/associations/collection_association.rb:461:in `block in create_record'
from path/associations/collection_association.rb:152:in `block in transaction'
from path/connection_adapters/abstract/database_statements.rb:213:in `block in transaction'
from path/connection_adapters/abstract/database_statements.rb:221:in `within_new_transaction'
from path/connection_adapters/abstract/database_statements.rb:213:in `transaction'
from path/transactions.rb:209:in `transaction'
from path/associations/collection_association.rb:151:in `transaction'
from path/associations/collection_association.rb:460:in `create_record'
from path/associations/collection_association.rb:121:in `create'
from path/associations/collection_proxy.rb:260:in `create'
from (irb):14
from ~/.rvm/gems/ruby-head/gems/railties-4.0.4/lib/rails/commands/console.rb:90:in `start'
from ~/.rvm/gems/ruby-head/gems/railties-4.0.4/lib/rails/commands/console.rb:9:in `start'
from /.rvm/gems/ruby-head/gems/railties-4.0.4/lib/rails/commands.rb:62:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'
