I've read lots about self referential classes in Rails, but am still having problems getting them working.
I have a class of Articles and I want them to be able to refer to each other, from a source article to an outcome article - and then be able to find the reverse. So I'm trying to do a has_many through, using another class called Links.
My schema is
create_table "articles", :force => true do |t|
t.string "name"
t.text "body"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "links", :force => true do |t|
t.integer "source_id"
t.integer "outcome_id"
t.string "question"
t.datetime "created_at"
t.datetime "updated_at"
end
The models are
class Article < ActiveRecord::Base
has_many :links_as_source, :foreign_key => "source_id", :class_name => "Link"
has_many :sources, :through => :links_as_source
has_many :links_as_outcome, :foreign_key => "outcome_id", :class_name => "Link"
has_many :outcomes, :through => :links_as_outcome
end
and
class Link < ActiveRecord::Base
belongs_to :source, :foreign_key => "source_id", :class_name => "Article"
belongs_to :outcome, :foreign_key => "outcome_id", :class_name => "Article"
end
I can create articles in the console, and I can link articles together, using a.outcomes << b but the link table is only storing the outcome_id, not the source_id.
What am I doing wrong?
I got this to work in the end. I changed the names - I don't know if that mattered. I did read somewhere that source was a silly name to use for something.
So this is what works:
My schema
create_table "article_relationships", :force => true do |t|
t.integer "parent_id"
t.integer "child_id"
...
end
create_table "articles", :force => true do |t|
t.string "name"
...
end
My article model
has_many :parent_child_relationships,
:class_name => "ArticleRelationship",
:foreign_key => :child_id,
:dependent => :destroy
has_many :parents,
:through => :parent_child_relationships,
:source => :parent
has_many :child_parent_relationships,
:class_name => "ArticleRelationship",
:foreign_key => :parent_id,
:dependent => :destroy
has_many :children,
:through => :child_parent_relationships,
:source => :child
Related
How in rails 4.1 enum prescribe in migration something like this?
class CreateFriendsUsers < ActiveRecord::Migration
def change
create_table :friends_users, id: false do |t|
t.integer :friend_id
t.integer :user_id
t.integer :status, [:active, :deactive]
end
end
end
this is join table for user and user
has_and_belongs_to_many :friends,
:class_name => "User",
:foreign_key => "user_id",
:association_foreign_key => "friend_id",
:join_table => "friends_users",
:after_add => :add_friend,
:after_remove => :remove_friend
I am trying to save a person's Facebook friends into my database. I want to store the Facebook users in a table and then store their friendships in another table. The friendships would have the integer of the FacebookUser that requested the friendship and the integer of the friend, both of which are foreign keys to the facebook_users table. However I keep getting this message when I try to link the a user's facebook friends with friendships.
Error
ActiveRecord::HasManyThroughSourceAssociationNotFoundError: Could not find the source association(s) :friend or :friends in model Friendship. Try 'has_many :friends, :through => :friendships, :source
=> <name>'. Is it one of :FacebookUser or :FacebookFriend?
friendship.rb
class Friendship < ActiveRecord::Base
attr_accessible :facebook_user_id, :facebook_friend_id
belongs_to :FacebookUser
belongs_to :FacebookFriend, :class_name => :FacebookUser
end
facebook_user.rb
class FacebookUser < ActiveRecord::Base
attr_accessible :first_name, :gender, :last_name
has_many :friendships, :foreign_key => :facebook_user_id
has_many :friends, :through => :friendships, :source => :FacebookUser
end
Schema
create_table "facebook_users", :force => true do |t|
t.string "first_name"
t.string "last_name"
t.string "gender"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
create_table "friendships", :force => true do |t|
t.integer "facebook_user_id"
t.integer "facebook_friend_id"
end
the convention Rails uses is to use associations as defined by the class name and the foreign key. if you've set up your tables like above, you should change your models to the following.
class Friendship < ActiveRecord::Base
attr_accessible :facebook_user_id, :facebook_friend_id
belongs_to :facebook_user # implies a foreign key of facebook_user_id and class of FacebookUser
belongs_to :facebook_friend, class_name: 'FacebookUser' #implies a foreign key of facebook_friend_id
end
class FacebookUser < ActiveRecord::Base
attr_accessible :first_name, :gender, :last_name
has_many :friendships
has_many :friends, :through => :friendships, :source => :facebook_friend
end
I'm currently working on my first project and am trying to add "friending" to my app. However, I'm having a little trouble grasping the concept of the friendships model, since attributes that don't seem to exist in my database seem to just work.
I have my model and database columns listed below. I understand that this is a join table, but in the user model where do friends, requested_friends, and pending friends come from if they don't exist in the friendships table? Is it because it is a virtual join table so that I could just add whatever columns I need without having to migrate them?
Also, the tutorial eventually does #user.pending_friends.each even though that column doesn't exist in my users table. I'm pretty confused on this part.
Currently I'm going through this brief tutorial: http://railsforum.com/viewtopic.php?id=16760
Here are my files:
user model
class User < ActiveRecord::Base
...
...
has_many :friendships, :dependent => :destroy
has_many :friends, :through => :friendships, :conditions => "status = 'accepted'"
has_many :requested_friends, :through => :friendships, :source => :friend, :conditions => "status = 'requested'", :order => :created_at
has_many :pending_friends, :through => :friendships, :source => :friend, :conditions => "status = 'pending", :order => :created_at
end
friendship model
class Friendship < ActiveRecord::Base
attr_accessible :friend_id
belongs_to :user
belongs_to :friend, :class_name => "User"
end
schema
create_table "friendships", :force => true do |t|
t.integer "user_id"
t.integer "friend_id"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
create_table "users", :force => true do |t|
t.string "name"
t.string "email"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
t.string "password_digest"
t.string "remember_token"
end
You probably forgotten to migrate since you don't have status column in your schema. Associations you're referring is bound to friend_id key that exist in friendships table. Last 2 associations is just using foreign key defined for belongs_to :friend. Please have a look here. I guess such associations can work without actual attribute if this is what you meant, you just don't get condition: functionality here and all 3 last associations will return same values.
In my Rails 3 project, I have a user model with a self referential join, through the follow model. I want to use this join table to find activity related to the followed user. I have almost everything set up correctly, except that the query generated by the join is totally ignoring the :primary_key option on the join model.
Here is the relevant schema for the relevant models:
create_table "users", :force => true do |t|
t.string "email", :default => "", :null => false
t.string "first_name"
t.string "last_name"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "follows", :force => true do |t|
t.integer "user_id"
t.integer "followed_user_id"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "activities", :force => true do |t|
t.integer "user_id"
t.text "body"
t.datetime "created_at"
t.datetime "updated_at"
end
Here's the associations in the models
class User < ActiveRecord::Base
has_many :follows
has_many :followed_users, :through => :follows
has_many :followed_activities, :through => :follows
has_many :activities
end
class Follow < ActiveRecord::Base
belongs_to :user
belongs_to :followed_user, :class_name => "User"
has_many :followed_activities, :primary_key => :followed_user, :foreign_key => :user_id, :class_name => "Activity"
end
The following work just fine:
u = User.first
u.follows # returns corresponding records from the follows table
u.followed_users # returns all users that u is following
u.followed_users.first.activities # returns all activity records corresponding to the first person the user is following
Follow.first.activities # same as the previous
However, the following just returns an empty array:
u.followed_activities
Here is the sql that is generated from the last statement:
Activity Load (0.2ms) SELECT `activities`.* FROM `activities` INNER JOIN `follows` ON `activities`.user_id = `follows`.id WHERE ((`follows`.user_id = 1))
The reason it isn't working is because it is trying to join use 'follows'.id as the primary key rather than 'follows'.followed_user.
Is this a bug, or do I have to repeat the :primary_key declaration somewhere on the user model? I can't find any mention anywhere in the Rails api, or anywhere else online.
Rails Version: 3.0.7
I've found it intuitive to daisy chain relationships with the 'nested_has_many_through' gem, http://rubygems.org/gems/nested_has_many_through which will be a standard part of rails 3.1 and could give you another tool to tackle the issue here
It will let you do something like this:
class Author < User
has_many :posts
has_many :categories, :through => :posts, :uniq => true
has_many :similar_posts, :through => :categories, :source => :posts
has_many :similar_authors, :through => :similar_posts, :source => :author, :uniq => true
has_many :posts_of_similar_authors, :through => :similar_authors, :source => :posts, :uniq => true
has_many :commenters, :through => :posts, :uniq => true
end
class Post < ActiveRecord::Base
belongs_to :author
belongs_to :category
has_many :comments
has_many :commenters, :through => :comments, :source => :user, :uniq => true
end
This has super-simplified my queries and collections. I hope you find an answer to your problem, it's a tough one!
Justin, you have 2 associations called "followed_activities". sure, they have different context (different models), but I'd like to ask you to try method inside the association block like this:
has_many :followed_users, :through => :follows do
def activities
end
end
I would like to join more than three tables in Rails 3.
My code is
class offer < ActiveRecord::Base
belongs_to :user
has_many :usercomments, :dependent => :destroy
has_many :comments, :through => :usercomments, :dependent => :destroy
end
class User < ActiveRecord::Base
has_many :usercomments, :dependent =>:destroy
has_many :comments,:through => :usercomments, :dependent => :destroy
has_many :offers, :dependent => :destroy
end
class Usercomment < ActiveRecord::Base
belongs_to :user
belongs_to :comment
belongs_to :offer
end
class Comment < ActiveRecord::Base
has_one :usercomment, :dependent => :destroy
has_one :offer, :through => :usercomments
has_one :user, :through => :usercomments
end
My schema is:
create_table "offers", :force => true do |t|
t.integer "step_id"
t.integer "user_id"
t.date "offerdate"
end
create_table "users", :force => true do |t|
t.string "firstname", :limit => 100, :default => ""
t.string "lastname", :limit => 100, :default => ""
t.string "email", :limit => 100
end
create_table "usercomments", :force => true do |t|
t.integer "user_id"
t.integer "airoffer_id"
t.integer "comment_id"
t.boolean "shared"
end
create_table "comments", :force => true do |t|
t.string "comment"
t.datetime "created_at"
t.datetime "updated_at"
end
and index.html.erb is:
<% airoffers.each do |airoffer| %>
???
<% end %>
In my html.erb page I would like to find a comment for an offer (offer_id) and an user (user_id).
It looks to me like what you want is:
class User < ActiveRecord::Base
has_many :comments
has_many :offers
end
class Offer < ActiveRecord::Base
has_many :comments
belongs_to :user
end
class Comment < ActiveRecord::Base
belongs_to :user
belongs_to :offer
end
If you want all the Comments that belong to a specific User and a specific Offer, just do Comment.where(:user_id => # :offer_id => #) and pass in the User and Offer you want.
Does this help?
This will give you an array of comments for User#123 en Offer#456
UserComment.find(:all, :conditions => {
:user_id => 123,
:offer_id => 456
}).collect(&:comment)
I would use it this way:
Comment.find(
:all,
:conditions => {
:user_id => 123,
:offer_id => 456
},
:join => :usercomment
)
OR:
Comment.find(
:all,
:conditions => [
"usercomments.user_id = ? AND usercomments.offer_id = ?",
123,
456
],
:join => :usercomment
)
Rails have a lot of beautiful ways to write queries.
Finally, i chose this solution
my code
class offer < ActiveRecord::Base
belongs_to :user
has_many :comments, :dependent => :destroy, :order => "updated_at DESC"
end
class User < ActiveRecord::Base
has_many :comments,:dependent => :destroy
has_many :offers, :dependent => :destroy
end
class Comment < ActiveRecord::Base
has_one :user, :dependent => :destroy
has_one :airoffer, :dependent => :destroy
end
schema
create_table "offers", :force => true do |t|
t.integer "user_id"
t.date "offerdate"
end
create_table "users", :force => true do |t|
t.string "firstname", :limit => 100, :default => ""
t.string "lastname", :limit => 100, :default => ""
t.string "email", :limit => 100
end
create_table "comments", :force => true do |t|
t.integer "user_id"
t.integer "offer_id"
t.string "comment"
t.datetime "created_at"
t.datetime "updated_at"
end
in offer_controller.rb
#offers = User.find(current_user.id).offers.includes(:comments)
and in my index.html.erb
<% #offers.each do |airoffer| %>
<% airoffer.comments[0].comment %>
<% end %>
I know, it's not the better solution, but in the first time i will use it.