There is a model relation like this.
class A
belongs_to :ref_config,:class_name => 'User'
end
My question is :
the A has a attribute named flag, now i want to create a function like this:
if flag == 1, I want the class A like this belongs_to :ref_config,:class_name => 'Department and if flag == 2, i want the class A like this belongs_to :ref_config,:class_name => 'User'
How can I implement the function
Thank you!
Have a look at polymorphic associations, which will let you use the same belongs_to relation to refer to different models.
You could configure your models something like this:
class A < ActiveRecord::Base
belongs_to :ref_config, :polymorphic => true
end
class Department < ActiveRecord::Base
has_many :as, :as => :ref_config
end
class User < ActiveRecord::Base
has_many :as, :as => :ref_config
end
To set up the needed columns in the A table, use a migration like this:
class CreateAs < ActiveRecord::Migration
def self.up
create_table :as do |t|
t.string :name # or whatever other attributes A should have
t.references :ref_config, :polymorphic => true
end
end
def self.down
drop_table :as
end
end
From the little i got your question following may help you.
class A
belongs_to :department_config, :class_name => 'Department', :conditions=> flag= 1
belongs_to :user_config, :class_name => 'User', :conditions=> flag= 2
end
Related
I'm trying to gain a value from an associated table linked via a field in a table using the following (where i is created in an each loop):
value = current_user.question["convq#{i}"].id
My table has references from the Questions table to a Questionsbank table in the form of columns named convq1_id, convq2_id ... convq3_id.
I simply want to cycle through each field in Questions and gain the questionbank.text field.
Sadly, the above will only give me the physical value in the question table field not a link to the associated record using the following code:
(1...9).each do |i|
value = current_user.question["convq#{i}"].id
end
Can anyone let me know how I can cycle through table and gain the associated 'id' or text value of the referenced record?
Thanks in advance.
Each model is set up as:
class Question < ActiveRecord::Base
belongs_to :user
belongs_to :convq1, :class_name => 'Questionbank'
belongs_to :convq2, :class_name => 'Questionbank'
belongs_to :convq3, :class_name => 'Questionbank'
belongs_to :convq4, :class_name => 'Questionbank'
belongs_to :convq5, :class_name => 'Questionbank'
belongs_to :convq6, :class_name => 'Questionbank'
belongs_to :convq7, :class_name => 'Questionbank'
belongs_to :convq8, :class_name => 'Questionbank'
belongs_to :convq9, :class_name => 'Questionbank'
has_many :questionbanks
end
and ...
class Questionbank < ActiveRecord::Base
has_many :likes
has_many :questions
end
I think this is what you might be looking for:
(1...9).each do |i|
value = current_user.question["convq#{i}"]
questionbank = Questionbank.find_by( question: "{value}")
questionbank.id
end
I recently made the following models:
class User < ActiveRecord::Base
has_many :resources
has_many :resource_views, :through => :user_resource_views, :source => 'Resource'
end
class Resource < ActiveRecord::Base
belongs_to :user
has_many :resource_views, :through => :user_resource_views, :source => 'Resource'
end
class UserResourceView < ActiveRecord::Base
attr_accessible :resource_id, :user_id
belongs_to :resource
belongs_to :user_id
end
Now, I want my home#index action to set #resources to the current_user's most recently viewed resources. How would you advise I proceed? Perhaps something similar to current_user.resource_views.find(:all, :order => 'created_at')?
In SQL, I would do something like:
SELECT *
FROM Resource
WHERE id IN (SELECT * FROM UserResourceView WHERE user_id = current_user.id)
... but then the ORDER BY created_at, hmmm
I'll be periodically adding progress updates throughout the day until I figure it out.
Given you're on Rails 3.x, what you're looking for is probably something like this:
class User < ActiveRecord::Base
has_many :resources
has_many :resource_views, :class_name => 'UserResourceView'
has_many :viewed_resources, :through => :resource_views, :source => :resource
def recently_viewed_resources
viewed_resources.order('user_resource_views.created_at DESC')
end
end
class Resource < ActiveRecord::Base
belongs_to :user
has_many :resource_views, :class_name => 'UserResourceView'
end
class UserResourceView < ActiveRecord::Base
attr_accessible :resource_id, :user_id
belongs_to :resource
belongs_to :user_id
end
And to access the collection in your controller:
current_user.recently_viewed_resources
In Rails 3 I'm trying to model a user content system, where the user can post different types of content, for example, note, photo, url etc.
From a Java/C# OO perspective, I would use a polymorphic relationship between the User and an interface representing a Content item, e.g. something called IUserContent.
I'm struggling to find an example that works how I expect it to, here's what I tried first, in short I'm getting confused about the implementation of polymorphic associations in ActiveRecord.
# user.rb model - includes...
has_many :notes, :as => :postable, :dependent => :destroy, :inverse_of => :postable
has_many :urls, :as => :postable, :dependent => :destroy, :inverse_of => :postable
has_many :photos, :as => :postable, :dependent => :destroy, :inverse_of => :postable
# url.rb ...
belongs_to :postable, :polymorphic => true, :inverse_of => :urls
# photo.rb
belongs_to :postable, :polymorphic => true, :inverse_of => :photos
# note.rb
belongs_to :postable, :polymorphic => true, :inverse_of => :notes
I'm still just following examples I've found, and frankly this feels like User is the polymorphic target, not the content.
I think I want something like this...
# within user.rb
has_many :postable, :as => :postable, dependent => :destroy, :inverse_of => :users
# photo.rb
# url.rb
# note.rb
# all have the following...
belongs_to :user, :polymorphic => true, :inverse_of => :postable
... looking for a few pointers in the right direction.
Thank you.
The only way you can do that is if all of these classes inherit from the same base class, as in:
class User < ActiveRecord::Base
has_many :postable, :as => :postable, :dependent => :destroy, :class_name => 'Postable'
end
class Postable < ActiveRecord::Base
belongs_to :user, :polymorphic => true
end
class Photo < Postable
end
class Url < Postable
end
class Note < Postable
end
So, you have to use the ActiveRecord single-table inheritance to model such a relationship.
I have a rails 3.0
has_many :X, :through => :something set up and i have a custom validator that does some custom validation on some complicated logic. I want to when you add anything to this many to many relationship both models are valid?
Project Class:
class Project < ActiveRecord::Base
has_many :assignments
has_many :users, :through => :assignments
validates :name, :presence => true
end
Assignment:
class Assignment < ActiveRecord::Base
belongs_to :project
belongs_to :user
end
User class with custom validator:
class MyCustomValidator < ActiveModel::Validator
def validate( record )
if record.projects.length > 3
record.errors[:over_worked] = "you have to many projects!"
end
end
end
class User < ActiveRecord::Base
has_many :assignments
has_many :projects, :through => :assignments
validates :name, :presence => true
validates_with MyCustomValidator
end
What i really want to do is prevent each model from invalidating the other so to say
prevent
my_user.projects << fourth_project
and
my_project.users << user_with_four_projects_already
from happening. Right now it allows the assignment and just the user becomes invalid.
class Project < ActiveRecord::Base
has_many :assignments
has_many :users, :through => :assignments
validates :name, :presence => true
validates_associated :users
end
According to the docs, users must already be assigned to Projects in order to be validated. So:
my_user.projects << fourth_project
would occur, then projects would validate the user and see that it is indeed invalid, making the project invalid as well as in the inverse example.
Ok so here goes. I don't know if I'm over complicating things or if I'm just still so new to Rails that I don't understand the basics. What I want in sudo code is this:
User
has_many projects as owner through relationship
has_many projects as contributor through relationship
has_many projects as follower through relationship
Project
has_one user as owner through relationship
has_many users as followers through relationship
has_many users as contributors through relationship
Relationship
belongs_to user
belongs_to project
Then I'm wanting to have the following magical things:
owner = Project.owner
followers = Project.followers
contributors = Project.contributors
projects = User.projects
myprojects = User.projects... (now I'm really not sure)
followedProjects = ...
contributingProjects = ...
So in writing that down I can see that there is another gap in my understanding of this model. The users can have the role of owner, follower or contributor or any combination of all three.
In terms of real code I have added here what I think is the relevant parts:
class User < ActiveRecord::Base
has_many :user_project_relationships, :as => :relateable, :class_name => "UserProjectRelationship"
has_many :projects, :as => :owner, :through => :relateable, :class_name => "Project", :source_type => :owner
has_many :projects, :as => :follower, :through => :relateable, :class_name => "Project", :source_type => :follower
has_many :projects, :as => :contributor, :through => :relateable, :class_name => "Project", :source_type => :contributor
end
class Project < ActiveRecord::Base
has_many :user_project_relationships, :as => :relateable, :class_name => "UserProjectRelationship"
has_one :user, :as => :owner, :through => :relateable, :class_name => "User"
has_many :users, :as => :followers, :through => :relateable, :source_type => :follower, :class_name => "User"
has_many :users, :as => :contributors, :through => :relateable, :source_type => :contributor, :class_name => "User"
end
class UserProjectRelationship < ActiveRecord::Base
belongs_to :user
belongs_to :project, :polymorphic => true
end
The migration for the relationships model is:
class CreateUserProjectRelationships < ActiveRecord::Migration
def self.up
create_table :user_project_relationships do |t|
t.integer :relateable_id
t.string :relateable_type
t.integer :project_id
t.timestamps
end
add_index :user_project_relationships, [:relateable_id, :relateable_type], :name => :relateable
add_index :user_project_relationships, :project_id
end
def self.down
drop_table :user_project_relationships
end
end
Currently I get errors for things like project.users ActiveRecord::HasManyThroughAssociationNotFoundError: Could not find the association :relateable in model Project
I feel like I'm too in the wilderness here to really get what I want, and maybe relying on magical rails to do more than it does. Any guidance on the best path would be greatly appreciated.
Thanks in advance
Steve
Rails can do alot, but I think instead you're trying to make the Relationship model do too much. Each of those are a different kind of relationship, so I think try to keep them so.
Split that up into separate join models:
class User < ActiveRecord::Base
has_many :owned_projects, :class_name => "Project", :foreign_key => :owner_id
has_many :projects_followers
has_many :followed_projects, :class_name => "Project", :through => :projects_followers
has_many :projects_contributors
has_many :contributed_projects, :class_name => "Project", :through => :projects_contributors
end
class Project < ActiveRecord::Base
belongs_to :owner
has_many :projects_followers
has_many :followers, :class_name => "User", :through => :projects_followers
has_many :projects_contributors, :foreign_key => :contributor_id
has_many :contributors, :class_name => "User", :through => :projects_contributors
end
class ProjectsFollowers < ActiveRecord::Base
belongs_to :user
belongs_to :project
end
class ProjectsContributors < ActiveRecord::Base
belongs_to :user
belongs_to :project
end
Should be a lot closer to what you want. You can then indeed do
project.owner
project.followers
project.contributors
and
user.owned_projects
user.followed_projects
user.contributed_projects
That should either work, or get you pretty close.
I think your mixup came from trying to make a polymorphic relationship, which I don't think is desireable here. AFAI grok, the use case for polymorphic relationships is when you want 1 Model to be related to Any number of other models in the same way. That's not the case here, as you have 2 models with 3 different types of relationships between them.