Using Rails 3.2. I have the following code:
# photo.rb
class Photo < ActiveRecord::Base
after_create :associate_current_user
private
def associate_current_user
current_user = UserSession.find.user
self.user_id = current_user.id
end
end
Before a new record is created, it searches for the current_user. This is alright if it's just 1 new record at a time. But if there are 100 records to be created, it's gonna search for the same current_user 100 times. There is definitely performance issue.
Is there a way I can cache the object for similar operation, or any suggestion?
Thanks.
you can do memoization, something as follow
class Photo < ActiveRecord::Base
extend ActiveSupport::Memoizable
after_create :associate_current_user
private
def associate_current_user
current_user = UserSession.find.user
self.user_id = current_user.id
end
associate_current_user
end
Related
Rails 4, Ruby 2.3.1 (noob alert)
I have a restaurant reservation app. before a reservation is saved I need to check the db to ensure there is a table available. To do this I check the date and time selected in the form with a count:
Reservation.where(r_date:params[:r_date],r_time:params[:r_time]).count < 3
assuming the restaurant has 3 tables. If the count is more than 3 then there is not a table available.
How do I get the params from #reservation in the controller to the callback function in the model?
You can use a before_save method to check availability, and invalidate the model, canceling the save, if there are no tables available.
In your controller:
class ReservationsController < ApplicationController
def create
#reservation = Reservation.new(reservation_params)
if #reservation.save
redirect_to reservation_path(#reservation)
else
render 'new'
end
end
private
def reservation_params
params[:reservation].permit(:r_date, :r_time)
end
end
Then, in your model:
class Reservation < ActiveRecord::Model
before_save :check_availability
private
def check_availability
reservation_count = Reservation.where(r_date: self.r_date, r_time: self.r_time).count
if reservation_count > 3
return false
end
end
end
I haven't had a chance to test this code, so please let me know if you have any problems.
Edit: explanation
I'm using Devise and Rails 3.2.16. I want to automatically insert who created a record and who updated a record. So I have something like this in models:
before_create :insert_created_by
before_update :insert_updated_by
private
def insert_created_by
self.created_by_id = current_user.id
end
def insert_updated_by
self.updated_by_id = current_user.id
end
Problem is that I get the error undefined local variable or method 'current_user' because current_user is not visible in a callback. How can I automatically insert who created and updated this record?
If there's an easy way to do it in Rails 4.x I'll make the migration.
Editing #HarsHarl's answer would probably have made more sense since this answer is very much similar.
With the Thread.current[:current_user] approach, you would have to make this call to set the User for every request. You've said that you don't like the idea of setting a variable for every single request that is only used so seldom; you could chose to use skip_before_filter to skip setting the User or instead of placing the before_filter in the ApplicationController set it in the controllers where you need the current_user.
A modular approach would be to move the setting of created_by_id and updated_by_id to a concern and include it in models you need to use.
Auditable module:
# app/models/concerns/auditable.rb
module Auditable
extend ActiveSupport::Concern
included do
# Assigns created_by_id and updated_by_id upon included Class initialization
after_initialize :add_created_by_and_updated_by
# Updates updated_by_id for the current instance
after_save :update_updated_by
end
private
def add_created_by_and_updated_by
self.created_by_id ||= User.current.id if User.current
self.updated_by_id ||= User.current.id if User.current
end
# Updates current instance's updated_by_id if current_user is not nil and is not destroyed.
def update_updated_by
self.updated_by_id = User.current.id if User.current and not destroyed?
end
end
User Model:
#app/models/user.rb
class User < ActiveRecord::Base
...
def self.current=(user)
Thread.current[:current_user] = user
end
def self.current
Thread.current[:current_user]
end
...
end
Application Controller:
#app/controllers/application_controller
class ApplicationController < ActionController::Base
...
before_filter :authenticate_user!, :set_current_user
private
def set_current_user
User.current = current_user
end
end
Example Usage: Include auditable module in one of the models:
# app/models/foo.rb
class Foo < ActiveRecord::Base
include Auditable
...
end
Including Auditable concern in Foo model will assign created_by_id and updated_by_id to Foo's instance upon initialization so you have these attributes to use right after initialization, and they are persisted into the foos table on an after_save callback.
another approach is this
class User
class << self
def current_user=(user)
Thread.current[:current_user] = user
end
def current_user
Thread.current[:current_user]
end
end
end
class ApplicationController
before_filter :set_current_user
def set_current_user
User.current_user = current_user
end
end
current_user is not accessible from within model files in Rails, only controllers, views and helpers. Although , through class variable you can achieve that but this is not good approach so for that you can create two methods inside his model. When create action call from controller then send current user and field name to that model ex:
Contoller code
def create
your code goes here and after save then write
#model_instance.insert_created_by(current_user)
end
and in model write this method
def self.insert_created_by(user)
update_attributes(created_by_id: user.id)
end
same for other methods
just create an attribute accessor in the model and initialize it when your record is being saved in controller as below
# app/models/foo.rb
class Foo < ActiveRecord::Base
attr_accessor :current_user
before_create :insert_created_by
before_update :insert_updated_by
private
def insert_created_by
self.created_by_id = current_user.id
end
def insert_updated_by
self.updated_by_id = current_user.id
end
end
# app/controllers/foos_controller.rb
class FoosController < ApplicationController
def create
#foo = Foo.new(....)
#foo.current_user = current_user
#foo.save
end
end
Using Rails 3.2. I have the following code:
# photo.rb
class Photo < ActiveRecord::Base
before_create :associate_current_user
after_save :increase_user_photos_count
after_destroy :decrease_user_photos_count
private
def associate_current_user
current_user = UserSession.find.user
self.user_id = current_user.id
end
def increase_user_photos_count
current_user = UserSession.find.user
User.increment_counter(:photos_count, current_user.id)
end
def decrease_user_photos_count
current_user = UserSession.find.user
User.decrement_counter(:photos_count, current_user.id)
end
end
Before a new record is created, it searches for the current_user. This is alright if it's just 1 new record at a time. But if there are 100 records to be created, it's gonna search for the same current_user 100 times. There is definitely performance issue.
I don't want it to keep finding the current user every time a record is created/photos_count updated, etc.
After refactoring, does this affect other users who are also uploading their photos using their accounts?
Note: For some reasons, I can't use the counter_cache and photos_controller.rb because I am following this example: http://www.tkalin.com/blog_posts/multiple-file-upload-with-rails-3-2-paperclip-html5-and-no-javascript
Thanks.
Use this
def current_user
#current_user ||= UserSession.find.user
end
This will cache the value in the instance variable #current_user unless it's nil (first time in the request), in which case it will set it.
I would like to use an after_save callback to set the updated_by column to the current_user. But the current_user isn't available in the model. How should I do this?
You need to handle it in the controller. First execute the save on the model, then if successful update the record field.
Example
class MyController < ActionController::Base
def index
if record.save
record.update_attribute :updated_by, current_user.id
end
end
end
Another alternative (I prefer this one) is to create a custom method in your model that wraps the logic. For example
class Record < ActiveRecord::Base
def save_by(user)
self.updated_by = user.id
self.save
end
end
class MyController < ActionController::Base
def index
...
record.save_by(current_user)
end
end
I have implemented this monkeypatch based on Simone Carletti's advice, as far as I could tell touch only does timestamps, not the users id. Is there anything wrong with this? This is designed to work with a devise current_user.
class ActiveRecord::Base
def save_with_user(user)
self.updated_by_user = user unless user.blank?
save
end
def update_attributes_with_user(attributes, user)
self.updated_by_user = user unless user.blank?
update_attributes(attributes)
end
end
And then the create and update methods call these like so:
#foo.save_with_user(current_user)
#foo.update_attributes_with_user(params[:foo], current_user)
I have 3 tables
items (columns are: name , type)
history(columns are: date, username, item_id)
user(username, password)
When a user say "ABC" logs in and creates a new item, a history record gets created with the following after_create filter.
How to assign this username ‘ABC’ to the username field in history table through this filter.
class Item < ActiveRecord::Base
has_many :histories
after_create :update_history
def update_history
histories.create(:date=>Time.now, username=> ?)
end
end
My login method in session_controller
def login
if request.post?
user=User.authenticate(params[:username])
if user
session[:user_id] =user.id
redirect_to( :action=>'home')
flash[:message] = "Successfully logged in "
else
flash[:notice] = "Incorrect user/password combination"
redirect_to(:action=>"login")
end
end
end
I am not using any authentication plugin. I would appreciate if someone could tell me how to achieve this without using plugin(like userstamp etc.) if possible.
Rails 5
Declare a module
module Current
thread_mattr_accessor :user
end
Assign the current user
class ApplicationController < ActionController::Base
around_action :set_current_user
def set_current_user
Current.user = current_user
yield
ensure
# to address the thread variable leak issues in Puma/Thin webserver
Current.user = nil
end
end
Now you can refer to the current user as Current.user
Documentation about thread_mattr_accessor
Rails 3,4
It is not a common practice to access the current_user within a model. That being said, here is a solution:
class User < ActiveRecord::Base
def self.current
Thread.current[:current_user]
end
def self.current=(usr)
Thread.current[:current_user] = usr
end
end
Set the current_user attribute in a around_filter of ApplicationController.
class ApplicationController < ActionController::Base
around_filter :set_current_user
def set_current_user
User.current = User.find_by_id(session[:user_id])
yield
ensure
# to address the thread variable leak issues in Puma/Thin webserver
User.current = nil
end
end
Set the current_user after successful authentication:
def login
if User.current=User.authenticate(params[:username], params[:password])
session[:user_id] = User.current.id
flash[:message] = "Successfully logged in "
redirect_to( :action=>'home')
else
flash[:notice] = "Incorrect user/password combination"
redirect_to(:action=>"login")
end
end
Finally, refer to the current_user in update_history of Item.
class Item < ActiveRecord::Base
has_many :histories
after_create :update_history
def update_history
histories.create(:date=>Time.now, :username=> User.current.username)
end
end
The Controller should tell the model instance
Working with the database is the model's job. Handling web requests, including knowing the user for the current request, is the controller's job.
Therefore, if a model instance needs to know the current user, a controller should tell it.
def create
#item = Item.new
#item.current_user = current_user # or whatever your controller method is
...
end
This assumes that Item has an attr_accessor for current_user.
The Rails 5.2 approach for having global access to the user and other attributes is CurrentAttributes.
If the user creates an item, shouldn't the item have a belongs_to :user clause? This would allow you in your after_update to do
History.create :username => self.user.username
You could write an around_filter in ApplicationController
around_filter :apply_scope
def apply_scope
Document.where(:user_id => current_user.id).scoping do
yield
end
This can be done easily in few steps by implementing Thread.
Step 1:
class User < ApplicationRecord
def self.current
Thread.current[:user]
end
def self.current=(user)
Thread.current[:user] = user
end
end
Step 2:
class ApplicationController < ActionController::Base
before_filter :set_current_user
def set_current_user
User.current = current_user
end
end
Now you can easily get current user as User.current
The Thread trick isn't threadsafe, ironically.
My solution was to walk the stack backwards looking for a frame that responds to current_user. If none is found it returns nil. Example:
def find_current_user
(1..Kernel.caller.length).each do |n|
RubyVM::DebugInspector.open do |i|
current_user = eval "current_user rescue nil", i.frame_binding(n)
return current_user unless current_user.nil?
end
end
return nil
end
It could be made more robust by confirming the expected return type, and possibly by confirming owner of the frame is a type of controller...