Please tell me the way how to implement dynamic associative link, which is itself determined by the attribute model.
I have two engines(Tbitcoin, Tstripe) each of them have a table payment. The model User has pay_currency attribute, which is the managing.
class User < ActiveRecord::Base
has_many :payments, ~> { where "pay_currency = 'real'" } , class_name: Tstripe::Payment, foreign_key: :uid
has_many :payments, ~> { where "pay_currency = 'bitcoin'" } ,class_name: Tbitcoin::Payment, foreign_key: :uid
end
What are the ways to dynamically determine the engine using User.last.payments.create ?
I think that you need a regular method instead of has_many association which will find proper payments associated with the user according to pay_currency value. Example:
class User < ActiveRecord::Base
def payments
payment_class = case pay_currency
when "real"
Tstripe::Payment
when "bitcoin"
Tbitcoin::Payment
end
payment_class.for_user(self)
end
end
class Tstripe::Payment < ActiveRecord::Base
belongs_to :user
def self.for_user(user)
where(user_id: user.uid)
end
end
I'm sure I am just missing something simple, but have been racking my brain for the past few days over this.
I have a Booking and Review table, where the Booking has many Reviews. I can create the Review, but run through an error when trying to define roles of the user leaving and receiving the review.
Here are my models. The Review
class Review < ActiveRecord::Base
before_save :define_review_role
after_create :call_update_rating
belongs_to :booking
belongs_to :client, class_name: "User", primary_key: "client_id"
belongs_to :talent, class_name: "User", primary_key: "talent_id"
def define_review_role
if review_sender_id === self.booking.client_id
review_receiver_id = self.booking.talent_id
else
review_receiver_id = self.booking.client_id
end
self.update
end
def call_update_rating
user = User.find(self.review_receiver_id)
if review_receiver_id == self.booking.talent_id
user.update_talent_rating(self.rating)
else
user.update_client_rating(self.rating)
end
user.save
end
end
And the Booking model
class Booking < ActiveRecord::Base
# Start Validations
validates :amount, format: {with: /(\d{1,3})(\.\d{1,2})?/, :message => "field is invalid. Please enter a correct amount."}
belongs_to :user
belongs_to :client, class_name: "User", primary_key: "client_id"
belongs_to :talent, class_name: "User", primary_key: "talent_id"
has_many :reviews
has_many :sent_reviews, class_name: "Review", primary_key: "talent_id"
has_many :received_reviews, class_name: "Review", primary_key: "client_id"
def client
User.find(client_id)
end
def talent
User.find(talent_id)
end
end
I have been able to create the review just fine, and upon inspection I am finding that the review.review_receiver_id is being left blank. The define_review_role for some reason is not running, I have tried with before_create, after_save, after_create and no dice.
I know that this is not running because upon inspection, the review_receiver_id is being left blank.
I am also able to access the information through review.booking.talent_id, and review.booking.client_id, so the connections are there. I know I must be missing something but have no idea what.
Your method define_review_role running you only have badly written code. It should probably look something like this
def define_review_role
if review_sender_id === self.booking.client_id
self.review_receiver_id = self.booking.talent_id
else
self.review_receiver_id = self.booking.client_id
end
end
If you try to assign value without self the value is assigned to newly created local method instead of attribute of your Report class.
You also cannot call save or update on the end of this method because you are calling it with before_save callback. Methods save and update trigger it again and method gonna be called again and you create infinity loop.
I want to be able to use two columns on one table to define a relationship. So using a task app as an example.
Attempt 1:
class User < ActiveRecord::Base
has_many :tasks
end
class Task < ActiveRecord::Base
belongs_to :owner, class_name: "User", foreign_key: "owner_id"
belongs_to :assignee, class_name: "User", foreign_key: "assignee_id"
end
So then Task.create(owner_id:1, assignee_id: 2)
This allows me to perform Task.first.owner which returns user one and Task.first.assignee which returns user two but User.first.task returns nothing. Which is because task doesn't belong to a user, they belong to owner and assignee. So,
Attempt 2:
class User < ActiveRecord::Base
has_many :tasks, foreign_key: [:owner_id, :assignee_id]
end
class Task < ActiveRecord::Base
belongs_to :user
end
That just fails altogether as two foreign keys don't seem to be supported.
So what I want is to be able to say User.tasks and get both the users owned and assigned tasks.
Basically somehow build a relationship that would equal a query of Task.where(owner_id || assignee_id == 1)
Is that possible?
Update
I'm not looking to use finder_sql, but this issue's unaccepted answer looks to be close to what I want: Rails - Multiple Index Key Association
So this method would look like this,
Attempt 3:
class Task < ActiveRecord::Base
def self.by_person(person)
where("assignee_id => :person_id OR owner_id => :person_id", :person_id => person.id
end
end
class Person < ActiveRecord::Base
def tasks
Task.by_person(self)
end
end
Though I can get it to work in Rails 4, I keep getting the following error:
ActiveRecord::PreparedStatementInvalid: missing value for :owner_id in :donor_id => :person_id OR assignee_id => :person_id
TL;DR
class User < ActiveRecord::Base
def tasks
Task.where("owner_id = ? OR assigneed_id = ?", self.id, self.id)
end
end
Remove has_many :tasks in User class.
Using has_many :tasks doesn't make sense at all as we do not have any column named user_id in table tasks.
What I did to solve the issue in my case is:
class User < ActiveRecord::Base
has_many :owned_tasks, class_name: "Task", foreign_key: "owner_id"
has_many :assigned_tasks, class_name: "Task", foreign_key: "assignee_id"
end
class Task < ActiveRecord::Base
belongs_to :owner, class_name: "User"
belongs_to :assignee, class_name: "User"
# Mentioning `foreign_keys` is not necessary in this class, since
# we've already mentioned `belongs_to :owner`, and Rails will anticipate
# foreign_keys automatically. Thanks to #jeffdill2 for mentioning this thing
# in the comment.
end
This way, you can call User.first.assigned_tasks as well as User.first.owned_tasks.
Now, you can define a method called tasks that returns the combination of assigned_tasks and owned_tasks.
That could be a good solution as far the readability goes, but from performance point of view, it wouldn't be that much good as now, in order to get the tasks, two queries will be issued instead of once, and then, the result of those two queries need to be joined as well.
So in order to get the tasks that belong to a user, we would define a custom tasks method in User class in the following way:
def tasks
Task.where("owner_id = ? OR assigneed_id = ?", self.id, self.id)
end
This way, it will fetch all the results in one single query, and we wouldn't have to merge or combine any results.
Extending upon #dre-hh's answer above, which I found no longer works as expected in Rails 5. It appears Rails 5 now includes a default where clause to the effect of WHERE tasks.user_id = ?, which fails as there is no user_id column in this scenario.
I've found it is still possible to get it working with a has_many association, you just need to unscope this additional where clause added by Rails.
class User < ApplicationRecord
has_many :tasks, ->(user) {
unscope(:where).where(owner: user).or(where(assignee: user)
}
end
Rails 5:
you need to unscope the default where clause
see #Dwight answer if you still want a has_many associaiton.
Though User.joins(:tasks) gives me
ArgumentError: The association scope 'tasks' is instance dependent (the scope block takes an argument). Preloading instance dependent scopes is not supported.
As it is no longer possible you can use #Arslan Ali solution as well.
Rails 4:
class User < ActiveRecord::Base
has_many :tasks, ->(user){ where("tasks.owner_id = :user_id OR tasks.assignee_id = :user_id", user_id: user.id) }
end
Update1:
Regarding #JonathanSimmons comment
Having to pass the user object into the scope on the User model seems like a backwards approach
You don't have to pass the user model to this scope.
The current user instance is passed automatically to this lambda.
Call it like this:
user = User.find(9001)
user.tasks
Update2:
if possible could you expand this answer to explain what's happening? I'd like to understand it better so I can implement something similar. thanks
Calling has_many :tasks on ActiveRecord class will store a lambda function in some class variable and is just a fancy way to generate a tasks method on its object, which will call this lambda. The generated method would look similar to following pseudocode:
class User
def tasks
#define join query
query = self.class.joins('tasks ON ...')
#execute tasks_lambda on the query instance and pass self to the lambda
query.instance_exec(self, self.class.tasks_lambda)
end
end
I worked out a solution for this. I'm open to any pointers on how I can make this better.
class User < ActiveRecord::Base
def tasks
Task.by_person(self.id)
end
end
class Task < ActiveRecord::Base
scope :completed, -> { where(completed: true) }
belongs_to :owner, class_name: "User", foreign_key: "owner_id"
belongs_to :assignee, class_name: "User", foreign_key: "assignee_id"
def self.by_person(user_id)
where("owner_id = :person_id OR assignee_id = :person_id", person_id: user_id)
end
end
This basically overrides the has_many association but still returns the ActiveRecord::Relation object I was looking for.
So now I can do something like this:
User.first.tasks.completed and the result is all completed task owned or assigned to the first user.
Since Rails 5 you can also do that which is the ActiveRecord safer way:
def tasks
Task.where(owner: self).or(Task.where(assignee: self))
end
My answer to Associations and (multiple) foreign keys in rails (3.2) : how to describe them in the model, and write up migrations is just for you!
As for your code,here are my modifications
class User < ActiveRecord::Base
has_many :tasks, ->(user) { unscope(where: :user_id).where("owner_id = ? OR assignee_id = ?", user.id, user.id) }, class_name: 'Task'
end
class Task < ActiveRecord::Base
belongs_to :owner, class_name: "User", foreign_key: "owner_id"
belongs_to :assignee, class_name: "User", foreign_key: "assignee_id"
end
Warning:
If you are using RailsAdmin and need to create new record or edit existing record,please don't do what I've suggested.Because this hack will cause problem when you do something like this:
current_user.tasks.build(params)
The reason is that rails will try to use current_user.id to fill task.user_id,only to find that there is nothing like user_id.
So,consider my hack method as an way outside the box,but don't do that.
Better way is using polymorphic association:
task.rb
class Task < ActiveRecord::Base
belongs_to :taskable, polymorphic: true
end
assigned_task.rb
class AssignedTask < Task
end
owned_task.rb
class OwnedTask < Task
end
user.rb
class User < ActiveRecord::Base
has_many :assigned_tasks, as: :taskable, dependent: :destroy
has_many :owned_tasks, as: :taskable, dependent: :destroy
end
In result, we can use it so:
new_user = User.create(...)
AssignedTask.create(taskable: new_user, ...)
OwnedTask.create(taskable: new_user, ...)
pp user.assigned_tasks
pp user.owned_tasks
I wrote this to count the number of responses (to a post) by unique users:
p = Post.find 1
r = p.responses.count(:user_id, distinct: true)
I tried translating it to a scope, but it throws an error: undefined method 'default_scoped?' for 30:Fixnum
class Response < ActiveRecord::Base
belongs_to :author, class_name: 'User', foreign_key: 'user_id'
belongs_to :post
scope :by_unique_users, joins(:post).count(:user_id, distinct: true)
end
class Post < ActiveRecord::Base
belongs_to :user
has_many :responses
end
class User < ActiveRecord::Base
has_many :posts
has_many :responses
end
From http://guides.rubyonrails.org/active_record_querying.html#scopes:
All scope methods will return an ActiveRecord::Relation object which will allow for further methods (such as other scopes) to be called on it.
In other words the returned result set needs to be chain-able with other Active Record method calls; calculations aren't chain-able, hence the error you're getting. With that said, if you absolutely want to use a scope we need to make it chain-able:
class Response < ActiveRecord::Base
scope :unique_responses_for_post, lambda {|post_id| where("post_id = ?", post_id).select(:user_id).uniq }
end
You can change the name as needed, I named it according to what it does. With that new scope defined you can do:
p = Post.find 1
r = Responses.unique_responses_for_post(p.id).count()
Alternatively
IMO, a more elegant solution for this problem would be to simply define an instance method inside your Post model:
def distinct_response_count
responses.count(:user_id, :distinct => true)
end
(This is not the actual code I'm using, although this sums up the idea of what I want to do)
class Connection < ActiveRecord::Base
belongs_to :connection1, :polymorphic => true
belongs_to :connection2, :polymorphic => true
end
class User < ActiveRecord::Base
has_many :followers, :class_name => 'Connection', :as => :connection1
has_many :followings, :class_name => 'Connection', :as => :connection2
end
My question is that I want to know how I will be able to create a method called "network" such that what is returned isn't an array. Like so,
u = User.first
u.network # this will return a merged version of :followings and :followers
So that I'll still be able to do this:
u.network.find_by_last_name("James")
ETA:
Or hmm, I think my question really boils down to if it is possible to create a method that will merge 2 has_many associations in such a way that I can still call on its find_by methods.
Are you sure that you want a collection of Connections, rather than a collection of Users?
If it's a collection of Connections that you need, it seems like you'll be well served by a class method on Connection (or scope, if you like such things).
connection.rb
class Connection < ActiveRecord::Base
class << self
def associated_with_model_id(model, model_id)
include([:connection1, :connection2]).
where("(connection1_type IS #{model} AND connection1_id IS #{model_id})
OR (connection2_type IS #{model} AND connection2_id IS #{model_id})")
end
end
end
user.rb
class User < ActiveRecord::Base
def network
Connection.associated_with_model_id(self.class.to_s, id)
end
end
Probably not as useful as you'd like, but maybe it'll give you some ideas.