Ahoy guys,
I'm new to Rails, and I feel like I'm definitely missing something crucial here, because it seems like this should be an easily solvable problem.
I've set up a Page model and a Coord model (with help from the getting started tutorial), and Coord successfully belongs_to Page. I'm trying to apply similar logic to make another model, Comment, belong to Coord, and only belong to Page via Coord.
Do I use :through for an association that (I think) only needs to link in one direction? As in Page < Coord < Comment?
At the moment I have:
class Page < ActiveRecord::Base
attr_accessible :description, :name
has_many :coords
has_many :comments, :through => :coords
end
Coord model:
class Coord < ActiveRecord::Base
belongs_to :page
has_many :comments
attr_accessible :coordinates, :x, :y
validates :x, :presence => true
validates :y, :presence => true
end
Then the Comment model:
class Comment < ActiveRecord::Base
belongs_to :coord
belongs_to :page
attr_accessible :body
end
I still keep getting errors about comments being an undefined method, or an association not being defined. Apologies if this is a common question, I don't personally know anyone who knows Rails, and the documentation only has examples too far removed from mine (to my knowledge). Thanks
Edit: added DB schema
ActiveRecord::Schema.define(:version => 20120712170243) do
create_table "comments", :force => true do |t|
t.text "body"
t.integer "coord_id"
t.integer "page_id"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
add_index "comments", ["coord_id"], :name => "index_comments_on_coord_id"
add_index "comments", ["page_id"], :name => "index_comments_on_page_id"
create_table "coords", :force => true do |t|
t.string "coordinates"
t.integer "x"
t.integer "y"
t.integer "page_id"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
add_index "coords", ["page_id"], :name => "index_coords_on_page_id"
create_table "pages", :force => true do |t|
t.string "name"
t.string "description"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
end
Page
class Page < ActiveRecord::Base
has_many :coords
has_many :comments, :through => :coords
end
Coord
class Coord < ActiveRecord::Base
belongs_to :page
has_many :comments
end
Comment
class Comment < ActiveRecord::Base
belongs_to :coord
has_one :page, :through => :coord
end
Using the above, you don't need page_id in the comments table.
Reference: A Guide to Active Record Associations
Related
I followed http://railscasts.com/episodes/17-habtm-checkboxes-revised?view=asciicast tutorial to set up a has_many through relationship and when I try to access information from one model it works but not from the other.
I can access the Category information from the Product model via #product.category_ids and #product.categories, but the reverse isn't true. I can't access the Product information from the Category model. Using #category.product_ids or #category.products gives me the error NoMethodError: undefined method 'product_ids' for #<Category:0x007fa70d430e98>
Product.rb
class Product < ActiveRecord::Base
attr_accessible :category_ids
has_many :categorizations
has_many :categories, through: :categorizations
accepts_nested_attributes_for :categorizations, :allow_destroy => true
end
Category.rb
class Category < ActiveRecord::Base
attr_accessible :product_ids
has_many :categorizations
has_many :products, through: :categorizations
end
-- EDIT --
Schema.rb
ActiveRecord::Schema.define(:version => 20130926192205) do
create_table "categories", :force => true do |t|
t.string "name"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
create_table "products", :force => true do |t|
t.string "name"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
create_table "categorization", :force => true do |t|
t.integer "product_id"
t.integer "category_id"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
add_index "categorization", ["product_id", "category_id"], :name => "index_categorization_on_product_id_and_category_id", :unique => true
add_index "categorization", ["product_id"], :name => "index_categorization_on_product_id"
add_index "categorization", ["category_id"], :name => "index_categorization_on_category_id"
end
To access the records from each object you should be able to:
#category.products
and
#product.categories
That will give you the associated objects.
product_ids is not a attribute on a category and it does not have accepts_attributes_for :products like your category model so removing attr_accessible :product_ids should fix the error.
I'm trying to use a :has_many :through type association, but I'm getting the following error:
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: work_units.developer_id:
Many other posts about this sort of thing have just had spelling mistakes, but I've checked mine.
class Developer < ActiveRecord::Base
attr_accessible :skype_name, :language_ids, :user_attributes
has_many :work_units
has_many :projects, :through => :work_units
...
end
class Project < ActiveRecord::Base
attr_accessible :complete, :description, :finalised, :price
has_many :work_units
has_many :developers, :through => :work_units
...
end
class WorkUnit < ActiveRecord::Base
attr_accessible :hours_worked
belongs_to :project
belongs_to :developer
end
I've run db:migrate and it didn't complain. I did make a mistake and had to rollback the db then re-migrate, but I think I did it right. I use the annotate gem and it doesn't show any of the relationship ids I'd expect. So, do I need to create a WorkUnits table or am I missing something? The rails guide didn't mention manually making tables.
Edit
Here's the migration I used to create the WorkUnit model and stuff:
class CreateWorkUnits < ActiveRecord::Migration
def change
create_table :work_units do |t|
t.integer :hours_worked, :default => 0
t.timestamps
end
end
end
Edit 2
Snippets from my schema.rb:
create_table "work_units", :force => true do |t|
t.integer "hours_worked", :default => 0
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
create_table "projects", :force => true do |t|
t.string "description"
t.decimal "price", :precision => 8, :scale => 2
t.boolean "complete", :default => false
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
Similarly for :developers. So, why doesn't my migration add the association information for me?
Your WorkUnit migration should look like this:
class CreateWorkUnits < ActiveRecord::Migration
def change
create_table :work_units do |t|
t.integer :hours_worked, :default => 0
t.references :developer
t.references :project
t.timestamps
end
add_index :work_units, :developer_id
add_index :work_units, :project_id
end
end
You need to add the foreign keys to your work_units table.
class CreateWorkUnits < ActiveRecord::Migration
def change
create_table :work_units do |t|
t.integer :hours_worked, :default => 0
t.integer :project_id, null: false
t.integer :developer_id, null: false
t.timestamps
end
add_index :work_units, :project_id
add_index :work_units, :developer_id
end
end
Another way:
class CreateWorkUnits < ActiveRecord::Migration
def change
create_table :work_units do |t|
t.integer :hours_worked, :default => 0
t.belongs_to :project
t.belongs_to :developer
t.timestamps
end
add_index :work_units, :project_id
add_index :work_units, :developer_id
end
end
You can also define these fields when generating your model, then they'll be added to the migration automatically as show in the second snippet.
$ rails g model WorkUnit hours_worked:integer project:belongs_to developer:belongs_to
Hope that helps.
A table for WorkUnit needs to exist, whether that means it migration was automatically generated via scaffolding or if the migration was manually written by you.
If you don't have a migration yet that creates that table, you'll need to create that migration because the table does need to exist.
You do need a work_units table with a project_id and developer_id column.
Have a look at http://xyzpub.com/en/ruby-on-rails/3.2/activerecord_datenbank_anlegen.html if you don't know how to create a table.
so i have 2 models:
create_table "holders", :force => true do |t|
t.string "faceid"
t.integer "badges_id"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
add_index "holders", ["badges_id"], :name => "index_holders_on_badges_id"
create_table "badges", :force => true do |t|
t.string "name"
t.text "description"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
i need 2 things:
to get all the badges of a certain faceid holder
to get all the holders of a certain badge.
i know its really noobs question but until now i didnt work with references so i dont really understood from the literature how to make the connection.
You actually need a many to many association on your holder and badge models. So you have to options either use has many :through or use has_and_belongs_to_many. The difference between the two can be found here. I am taking the example for has_many :through.
You need to create three models.
class Holder < ActiveRecord:Base
has_many :badges_holders
has_many :badges, :through => :badges_holders
end
class Badge < ActiveRecord:Base
has_many :badges_holders
has_many :holders, :through => :badges_holders
end
class BadgesHolder < ActiveRecord:Base
belongs :badge
belongs :holder
end
And your migration files needs to be:
create_table "holders", :force => true do |t|
t.string "faceid"
t.timestamps
end
add_index "holders", ["badges_id"], :name => "index_holders_on_badges_id"
create_table "badges", :force => true do |t|
t.string "name"
t.text "description"
t.timestamps
end
create_table "badges_holders", :force => true do |t|
t.integer "holder_id"
t.integer "badge_id"
t.timestamps
end
Now you can easily use Holder.find_by_faceid('xyz').badges to find the all hedges held by the holder whose faced is xyz. And Badge.first.holders to get all the holders for the first bedge.
For your question HABTM will be a good option as you do not need any extra field in the join table, so you can just use has_and_belongs_to_many in both of your models and you don't need BadgesHolder model in that case. And for the migration of the join table, replace first line with create_table "badges_holders", :id => false, :force => true do |t| a and remove t.timestamps as the join table for HABTM should not have any other column than the foreign keys.
If it's some Ruby on Rails, you must have 2 models :
class Holder < ActiveRecord:Base
has_many :badges
end
class Badge < ActiveRecord:Base
belongs_to :holder
end
Your entry called badges_id should not be in your holders table ; you should have a holder_id on your "badges" table.
Then, you can simply call
Holder.find_by_faceid('foobar').badges
and
Badge.find(1337).holder
If your badge can belongs to many holders, then you have to write a has_and_belongs_to_many relation.
My migration right now :
class CreateActivities < ActiveRecord::Migration
def self.up
create_table :activities do |t|
t.integer :account_id, :null => false
t.integer :target_id, :null => false
t.string :target_type, :null => false
t.string :event_type, :null => false
t.integer :employee_id
t.string :name
t.timestamps
end
add_index :activities, [:target_id, :target_type]
With this I can now call a target like so :
Activity.first.target
And it will bring up the target_id, based on the target_type.
How would I do the opposite of that so that I can select a target, and if it has any associated Activities, they will show up?
Like so :
Job.find(1234).activities
# Where Job.find(1234) is the target_id of many activities.
If I understand right, this should do it:
class Job < ActiveRecord::Base
has_many :activities, :conditions => ['target_type = ?', 'Job'], :as => :target
end
I have an Entry model and a Category model, where an Entry can have many Categories (through EntryCategories):
class Entry < ActiveRecord::Base
belongs_to :journal
has_many :entry_categories
has_many :categories, :through => :entry_categories
end
class Category < ActiveRecord::Base
has_many :entry_categories, :dependent => :destroy
has_many :entries, :through => :entry_categories
end
class EntryCategory < ActiveRecord::Base
belongs_to :category
belongs_to :entry
end
When creating a new Entry, I create it by calling #journal.entries.build(entry_params), where entry_params is the parameters from the entry form. If any categories are selected, however, I get this error:
ActiveRecord::HasManyThroughCantDissociateNewRecords in Admin/entriesController#create
Cannot dissociate new records through 'Entry#entry_categories' on '#'. Both records must have an id in order to delete the has_many :through record associating them.
Note that the '#' on the second line is verbatim; it doesn't output an object.
I have tried naming my categories selectbox on the form to categories and category_ids but neither make a difference; if either is in the entry_params, the save will fail. If no categories are selected, or I remove categories from entry_params (#entry_attrs.delete(:category_ids)), the save works properly, but the categories don't save, obviously.
It seems to me that the problem is that an EntryCategory record is attempting to be made before the Entry record is saved? Shouldn't build be taking care of that?
Update:
Here's the relevant parts of schema.rb, as requested:
ActiveRecord::Schema.define(:version => 20090516204736) do
create_table "categories", :force => true do |t|
t.integer "journal_id", :null => false
t.string "name", :limit => 200, :null => false
t.integer "parent_id"
t.integer "lft"
t.integer "rgt"
end
add_index "categories", ["journal_id", "parent_id", "name"], :name => "index_categories_on_journal_id_and_parent_id_and_name", :unique => true
create_table "entries", :force => true do |t|
t.integer "journal_id", :null => false
t.string "title", :null => false
t.string "permaname", :limit => 60, :null => false
t.text "raw_body", :limit => 2147483647
t.datetime "created_at", :null => false
t.datetime "posted_at"
t.datetime "updated_at", :null => false
end
create_table "entry_categories", :force => true do |t|
t.integer "entry_id", :null => false
t.integer "category_id", :null => false
end
add_index "entry_categories", ["entry_id", "category_id"], :name => "index_entry_categories_on_entry_id_and_category_id", :unique => true
end
Also, saving an entry with categories works fine in the update action (by calling #entry.attributes = entry_params), so it does seem to me that the problem is only based on the Entry not existing at the point that the EntryCategory records are attempted to be created.
I tracked down the cause of this error to be within the nested_has_many_through plugin. It seems that the version I had installed was buggy; after updating to the most recent version, my build works again.
Why do you call
self.journal.build(entry_params)
instead of
Entry.new(entry_params)
If you need to create a new entry associated to a specific Journal, given a #journal, you can do
#yournal.entries.build(entry_params)