Dynamically including a Rails Concern - ruby-on-rails

My objective is to dynamically load a set of methods to an ActiveRecord model instance based on an attribute that's set:
class Book < ActiveRecord::Base
after_initialize do |cp|
self.class.include "#{cp.subject}".constantize
end
end
I then have the following concerns:
module Ruby
extend ActiveSupport::Concern
def get_framework
'rails'
end
end
module Python
extend ActiveSupport::Concern
def get_framework
'django'
end
end
Then, when I run these separately, I get the correct framework string:
python_book = Book.create(:subject => 'python', :id => 1)
python_book.get_framework -> 'django'
ruby_book = Book.create(:subject => 'ruby', :id => 2)
ruby_book.get_framework -> 'rails'
My problem is that when I have both of the books returned in a query, the Concern is included is the last in the result set and is not picking up the correct Concern methods.
Books.all.order(:id => 'asc').collect do |book|
puts book.get_framework
end
# Result
['rails', 'rails']
I am assuming that this is because the 'include' is happening at the class level and not the instance level. Would love some help as to how to clean this up and make this work.

Use .extend
to add instance methods to a instances of Book instead.
Extends in action:
module Greeter
def say_hello
"Hello"
end
end
irb(main):008:0> a = Object.new
=> #<Object:0x00000101e01c38>
irb(main):009:0> a.extend(Greeter)
=> #<Object:0x00000101e01c38>
irb(main):010:0> a.say_hello
=> "Hello"
irb(main):011:0> Object.new.say_hello
NoMethodError: undefined method `say_hello' for #<Object:0x00000101e196d0>
class Book < ActiveRecord::Base
after_initialize do |cp|
self.extend subject.constantize
end
end

Related

Rails Module not loading for presenter

Why won't my module load properly when I include it in my presenter class?
My class methods and module methods are not available when loading from rails. The module works when loading out of rails in a single file.
app/presenters/body_parts/method_wrapper.rb
module BodyParts
def self.included(klass)
klass.extend ClassMethods # => Car
end # => :included
module ClassMethods
def set_wheels(*args)
x, *wheel_args = args # => [3], [3]
puts "Wheels class method called with: #{x.to_s}" # => nil, nil
#wheels |= x # => true, true
end # => :set_wheels
class MethodWrapper
attr_reader :klass # => nil
def initialize(klass)
#klass = klass
end # => :initialize
def wrap(method_name)
puts "Wrapping a method"
wrapper_callback(result)
end # => :wrap
end # => :wrap
end # => :wrap
private # => BodyParts
def wrapper_callback(result)
"Wrapped a #{result} in the call back"
end # => :wrapper_callback
end # => :wrapper_callback
app/presenters/car_presenter.rb
class CarPresenter
include BodyParts # => Car
set_wheels 3 # => true
def brand
'Car Brand' # => "Car Brand"
end # => :brand
set_wheels 3 # => true
def title # policy set to 2 for title methods because of the above
'Car Title'
end # => :title
end # => :title
car_presenter = CarPresenter.new # => #<CarPresenter:0x00fe4ed9300>
car_presenter.brand # => "Car Brand"
# >> Wheels class method called with: 3
# >> Wheels class method called with: 3
Binding.pry from CarsPresenter in Rails
[1] pry(CarPresenter)> set_wheels 3
NameError: undefined local variable or method `set_wheels' for CarPresenter:Class
from (pry):12:in `<class:CarPresenter>'
[2] pry(CarPresenter)> BodyParts
=> BodyParts
[3] pry(CarPresenter)> self
=> CarPresenter
Due to the way const loading works in rails, a module BodyParts should be defined in the top level of presenters directory, i.e. in app/presenters/body_parts.rb.rb.
Rails expects app/presenters/body_parts/method_wrapper.rb to define const BodyParts::MethodWrapper,
Read mode in rails guides.

NoMethodError: undefined method `liquidity_manager?' for #<Order:0x007fd9b7a4cf98>

My solution throws NoMethodError. This is what I have done below:
Order.rb
class Order < ActiveRecord::Base
belongs_to :member
end
Member.rb
class Order < ActiveRecord::Base
has_many :orders
def liquidity_manager?
#is_liquidity_manager ||= self.class.liquidity_managers.include?(self.email)
end
def liquidity_managers
ENV['LM_ACCOUNTS'].split(',')
end
end
rake task logic
The logic in lib/update_order_tags.rake
num_counts = (Order.count/10).ceil
num_counts.times do |i|
Order.all.offset(i*10).limit(10).find_each do |g|
if g.tags.blank? # am saving on only the blank fields
if g.liquidity_manager? # The error is here
g.tags = 'LM'
g.save!
else
g.tags = 'Customer'
g.save!
end
end
end
end
How do I reference the liquidity_manager? method to be useful for me in lib?
You defined Order#liquidity_manager? in Member.rb, which is not automatically loaded by Rails. You have to either explicitly load the file Member.rb, or rename that file to /app/models/order.rb.
So from the advise given to me by #sawa in the answer section, here is what I have done to make it work.
num_counts = (Order.count/10).ceil
num_counts.times do |i|
Order.all.offset(i*10).limit(10).find_each do |g|
if g.tags.blank?
if g.member.liquidity_manager? # So this easily gets to Member.rb to reference liquidity_manager? method.
g.tags = 'LM'
g.save!
else
g.tags = 'Customer'
g.save!
end
end
end
end

How to call custom method in ruby on rails 4?

I want to create a custom method, which I have defined in my questions_controller.rb file, as so:
def self.ping
#question = Question.first
#question.update(:amplify => #question.amplify + 1)
end
Now the problem is how do I call this method? Do I need to define a route first? How can I reference this from the console?
Thanks in advance.
I'd suggest to move it to your model:
question.rb
def self.ping
question = Question.first
question.update(:amplify => question.amplify + 1)
end
and define custom route, routes.rb
post '/ping' => 'questions#ping', as: 'ping'
questions_controller.rb
def ping
Question.ping
end
then you can reference it from console:
Question.ping
Please read this http://www.railstips.org/blog/archives/2009/05/11/class-and-instance-methods-in-ruby/
class Foo
def self.bar
puts 'class method'
end
def baz
puts 'instance method'
end
end
Foo.bar # => "class method"
Foo.baz # => NoMethodError: undefined method ‘baz’ for Foo:Class
Foo.new.baz # => instance method
Foo.new.bar # => NoMethodError: undefined method ‘bar’
Instead of
question.update(:amplify => question.amplify + 1)
You can use
question.increment!(:amplify)

rspec testing has_many :through and after_save

I have an (I think) relatively straightforward has_many :through relationship with a join table:
class User < ActiveRecord::Base
has_many :user_following_thing_relationships
has_many :things, :through => :user_following_thing_relationships
end
class Thing < ActiveRecord::Base
has_many :user_following_thing_relationships
has_many :followers, :through => :user_following_thing_relationships, :source => :user
end
class UserFollowingThingRelationship < ActiveRecord::Base
belongs_to :thing
belongs_to :user
end
And these rspec tests (I know these are not necessarily good tests, these are just to illustrate what's happening):
describe Thing do
before(:each) do
#user = User.create!(:name => "Fred")
#thing = Thing.create!(:name => "Foo")
#user.things << #thing
end
it "should have created a relationship" do
UserFollowingThingRelationship.first.user.should == #user
UserFollowingThingRelationship.first.thing.should == #thing
end
it "should have followers" do
#thing.followers.should == [#user]
end
end
This works fine UNTIL I add an after_save to the Thing model that references its followers. That is, if I do
class Thing < ActiveRecord::Base
after_save :do_stuff
has_many :user_following_thing_relationships
has_many :followers, :through => :user_following_thing_relationships, :source => :user
def do_stuff
followers.each { |f| puts "I'm followed by #{f.name}" }
end
end
Then the second test fails - i.e., the relationship is still added to the join table, but #thing.followers returns an empty array. Furthermore, that part of the callback never gets called (as if followers is empty within the model). If I add a puts "HI" in the callback before the followers.each line, the "HI" shows up on stdout, so I know the callback is being called. If I comment out the followers.each line, then the tests pass again.
If I do this all through the console, it works fine. I.e., I can do
>> t = Thing.create!(:name => "Foo")
>> t.followers # []
>> u = User.create!(:name => "Bar")
>> u.things << t
>> t.followers # [u]
>> t.save # just to be super duper sure that the callback is triggered
>> t.followers # still [u]
Why is this failing in rspec? Am I doing something horribly wrong?
Update
Everything works if I manually define Thing#followers as
def followers
user_following_thing_relationships.all.map{ |r| r.user }
end
This leads me to believe that perhaps I am defining my has_many :through with :source incorrectly?
Update
I've created a minimal example project and put it on github: https://github.com/dantswain/RspecHasMany
Another Update
Thanks a ton to #PeterNixey and #kikuchiyo for their suggestions below. The final answer turned out to be a combination of both answers and I wish I could split credit between them. I've updated the github project with what I think is the cleanest solution and pushed the changes: https://github.com/dantswain/RspecHasMany
I would still love it if someone could give me a really solid explanation of what is going on here. The most troubling bit for me is why, in the initial problem statement, everything (except the operation of the callback itself) would work if I commented out the reference to followers.
I've had similar problems in the past that have been resolved by reloading the association (rather than the parent object).
Does it work if you reload thing.followers in the RSpec?
it "should have followers" do
#thing.followers.reload
#thing.followers.should == [#user]
end
EDIT
If (as you mention) you're having problems with the callbacks not getting fired then you could do this reloading in the object itself:
class Thing < ActiveRecord::Base
after_save { followers.reload}
after_save :do_stuff
...
end
or
class Thing < ActiveRecord::Base
...
def do_stuff
followers.reload
...
end
end
I don't know why RSpec has issues with not reloading associations but I've hit the same types of problems myself
Edit 2
Although #dantswain confirmed that the followers.reload helped alleviate some of the problems it still didn't fix all of them.
To do that, the solution needed a fix from #kikuchiyo which required calling save after doing the callbacks in Thing:
describe Thing do
before :each do
...
#user.things << #thing
#thing.run_callbacks(:save)
end
...
end
Final suggestion
I believe this is happening because of the use of << on a has_many_through operation. I don't see that the << should in fact trigger your after_save event at all:
Your current code is this:
describe Thing do
before(:each) do
#user = User.create!(:name => "Fred")
#thing = Thing.create!(:name => "Foo")
#user.things << #thing
end
end
class Thing < ActiveRecord::Base
after_save :do_stuff
...
def do_stuff
followers.each { |f| puts "I'm followed by #{f.name}" }
end
end
and the problem is that the do_stuff is not getting called. I think this is the correct behaviour though.
Let's go through the RSpec:
describe Thing do
before(:each) do
#user = User.create!(:name => "Fred")
# user is created and saved
#thing = Thing.create!(:name => "Foo")
# thing is created and saved
#user.things << #thing
# user_thing_relationship is created and saved
# no call is made to #user.save since nothing is updated on the user
end
end
The problem is that the third step does not actually require the thing object to be resaved - its simply creating an entry in the join table.
If you'd like to make sure that the #user does call save you could probably get the effect you want like this:
describe Thing do
before(:each) do
#thing = Thing.create!(:name => "Foo")
# thing is created and saved
#user = User.create!(:name => "Fred")
# user is created BUT NOT SAVED
#user.things << #thing
# user_thing_relationship is created and saved
# #user.save is also called as part of the addition
end
end
You may also find that the after_save callback is in fact on the wrong object and that you'd prefer to have it on the relationship object instead. Finally, if the callback really does belong on the user and you do need it to fire after creating the relationship you could use touch to update the user when a new relationship is created.
UPDATED ANSWER **
This passes rspec, without stubbing, running callbacks for save (after_save callback included ), and checks that #thing.followers is not empty before trying to access its elements. (;
describe Thing do
before :each do
#user = User.create(:name => "Fred");
#thing = Thing.new(:name => 'Foo')
#user.things << #thing
#thing.run_callbacks(:save)
end
it "should have created a relationship" do
#thing.followers.should == [#user]
puts #thing.followers.inspect
end
end
class Thing < ActiveRecord::Base
after_save :some_function
has_many :user_following_thing_relationships
has_many :followers, :through => :user_following_thing_relationships, :source => :user
def some_function
the_followers = followers
unless the_followers.empty?
puts "accessing followers here: the_followers = #{the_followers.inspect}..."
end
end
end
ORIGINAL ANSWER **
I was able to get things to work with the after_save callback, so long as I did not reference followers within the body / block of do_stuff. Do you have to reference followers in the real method you are calling from after_save ?
Updated code to stub out callback. Now model can remain as you need it, we show #thing.followers is indeed set as we expected, and we can investigate the functionality of do_stuff / some_function via after_save in a different spec.
I pushed a copy of the code here: https://github.com/kikuchiyo/RspecHasMany
And spec passing thing* code is below:
# thing_spec.rb
require 'spec_helper'
describe Thing do
before :each do
Thing.any_instance.stub(:some_function) { puts 'stubbed out...' }
Thing.any_instance.should_receive(:some_function).once
#thing = Thing.create(:name => "Foo");
#user = User.create(:name => "Fred");
#user.things << #thing
end
it "should have created a relationship" do
#thing.followers.should == [#user]
puts #thing.followers.inspect
end
end
# thing.rb
class Thing < ActiveRecord::Base
after_save :some_function
has_many :user_following_thing_relationships
has_many :followers, :through => :user_following_thing_relationships, :source => :user
def some_function
# well, lets me do this, but I cannot use #x without breaking the spec...
#x = followers
puts 'testing puts hear shows up in standard output'
x ||= 1
puts "testing variable setting and getting here: #{x} == 1\n\t also shows up in standard output"
begin
# If no stubbing, this causes rspec to fail...
puts "accessing followers here: #x = #{#x.inspect}..."
rescue
puts "and this is but this is never seen."
end
end
end
My guess is that you need to reload your Thing instance by doing #thing.reload (I'm sure there's a way to avoid this, but that might get your test passing at first and then you can figure out where you've gone wrong).
Few questions:
I don't see you calling #thing.save in your spec. Are you doing that, just like in your console example?
Why are you calling t.save and not u.save in your console test, considering you're pushing t onto u? Saving u should trigger a save to t, getting the end result you want, and I think it would "make more sense" considering you are really working on u, not t.

undefined method 'link_to'

I'm writing a ruby-on-rails library module:
module Facets
class Facet
attr_accessor :name, :display_name, :category, :group, :special
...
URI = {:controller => 'wiki', :action => 'plants'}
SEARCH = {:status => WikiLink::CURRENT}
#Parameters is an hash of {:field => "1"} values
def render_for_search(parameters)
result = link_to(display_name, URI.merge(parameters).merge({name => "1"}))
count = WikiPlant.count(:conditions => (SEARCH.merge(parameters.merge({name => "1"}))))
result << "(#{count})"
end
end
...
end
when I call render_for_search I get the error
undefined method 'link_to'
I've tried requiring url_helper directly but can't figure out what's going wrong.
Try this:
ActionController::Base.helpers.link_to
This is because, ActionView urlhelpers are only available to the Views, not in your lib directory.
the link_to method is found in the ActionView::Helpers::UrlHelper module, plus you wou
so try this.
class Facet
include ActionView::Helpers::UrlHelper
...
end
Simply including the helper doesn't get you much further. The helpers assume that they are in the context of a request, so that they can read out the domain name and so on.
Do it the other way around; include your modules in the application helper, or something like that.
# lib/my_custom_helper.rb
module MyCustomHelper
def do_stuff
# use link_to and so on
end
end
# app/helpers/application_helper.rb
module ApplicationHelper
include MyCustomHelper
end

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