So I have some data that gets pulled from another rails app in a controller lets call it ExampleController and I want to validate it as being there in my model before allowing the wizard to move to its next step and I can't quite figure out how I should be doing it (I know that getting this data directly from the controller into the model violates MVC I am looking for the best workaround to get my data from the controller) . The data must come from the controller as the methods for getting it are contained in ApplicationController however I could do this in the Awizard controller if this is easier. (Also I cannot use a gem)
Please offer some kind of suggestion to the problem and not an explanation of why this is not the correct way to do things I realise that already but cannot do it another way.
The Example Controller
should this instead render the data then check it isn't blank elsewhere?
class ExampleController < ApplicationController
def valid_data?
data = #data could be nil or not
if data.blank?
return false
else
return true
end
end
My Model - (models/awizard.rb)
How do I use the valid_data? method from the example controller? in my validation here.
class AWizard
include ActiveModel::Validations
include ActiveModel::Conversion
include ActiveModel::Dirty
include ActiveModel::Naming
#This class is used to manage the wizard steps using ActiveModel (not ActiveRecord)
attr_accessor :id
attr_writer :current_step #used to write to current step
define_attribute_methods [:current_step] #used for marking change
validate :first_step_data, :if => lambda { |o| o.current_step == "step1" };
def first_step_data
#What should i put here to check the valid_data? from the examplecontroller
end
def initialize(attributes = {})
attributes.each do |name, value|
send("#{name}=", value)
end
end
def current_step
#current_step || steps.first
end
def steps
%w[step1 step2 step3] #make list of steps (partials)
end
def next_step
current_step_will_change! #mark changed when moving stepped
self.current_step = steps[steps.index(current_step)+1] unless last_step?
end
def previous_step
current_step_will_change! #mark changed when moving stepped
self.current_step = steps[steps.index(current_step)-1] unless first_step?
end
def first_step?
current_step == steps.first
end
def last_step?
current_step == steps.last
end
def all_valid?
steps.all? do |step|
self.current_step = step
valid?
end
end
def step(val)
current_step_will_change!
self.current_step = steps[val]
end
def persisted?
self.id == 1
end
end
Or do I need to add this to this view?
(/views/awizard/_step1.html.erb)
<div class="field">
<%= f.label 'Step1' %><br />
#This is the step I want to validate
</div>
I maybe have misunderstood the question since my answer is simple. However here's a solution that doesn't resort to metaprogramming, but to the fact that Wizard (the class not objects it creates ) is a singleton/constant.
class ExampleController < ApplicationController
def valid_data?
data = #data could be nil or not
result = data.blank?
Awizard.valid_data= result
result
end
end
class Wizard
cattr_accessor :valid_data
def valid_data?
self.class.valid_data
end
end
If course ExampleController#valid_data must have been called before you play around with a Wizard passing step_one.
UPDATE:Reasoning about the global state problem
(raised by #Valery Kvon)
The argument is that Wizard is global to the application and that #wizard instances will be dependant on a global state and are therefore badly encapsulated. But Data, coming from another site, is gloabl in the scope of your app. So there's no mismatch with Wizard beeing the one holding the data. On the contrary it can be considered as a feature.
One example. Wizards magic is only efficient at full moon.
Application SkyReport sends data :
:full_moon => true
It affects all wizards in stage 1 if they need to go on step2 of their power. Therefore relying on the global state of Wizard.valid_data? is exactly what we want...
However if each wizard has a personal message coming from Gandalf's application, then we'll want to inforce the invocation of Gandalf's data but then the solution is even simpler :
# in example_controller.rb
before_filter :set_wizard_data, :only => [:create, :update]
....
def set_wizard_data
#wizard = Wizard.find params[:id]
#wizard.valid_data= valid_data
end
But this again implies that Gandalf.app knows (something of) the #wizard and from how the problem is presented, data coming from the other site is pretty agnostic !
The issue here is that we don't know enough about the app, its requirements and underlying logic to decide what's good or not...
The only way to share controller level data with model is through external accessor.
Using metaprogramming you can trick the way to pass it to a model instance.
controller
def valid_data?
data = #data could be nil or not
result = data.blank? ? false : true
instance_eval <<-EOV
def AWizard.new(*args)
super(*args).tap {|aw| aw.external_valid = #{result}}
end
EOV
result
end
model
class AWizard
attr_accessor :external_valid
def initialize(attributes = {})
attributes.each do |name, value|
send("#{name}=", value)
end
end
validate :first_step_data, :if => lambda { |o| o.current_step == "step1" };
def first_step_data
# :external_valid would be true or false according to a valid_data?. Nil would be if valid_data? has not been called
if external_valid == false
errors.add ...
end
end
end
You can pass the data from the controller as a parameter to the validation method in the model.
In your models/awizard.rb
def valid_for_step_one?(some_external_data)
#validation logic here
end
So that in your controller, you can can call:
model.valid_for_step_one?(data_from_controller)
It would also be good if you can give a description of the data you are getting from the controller. How is it related to the model awizard?
Because another option is to set the external data as an attribute of the model. Then you can use it in your validation functions from there.
So I tried to edit and add to the #charlysisto question as this was closest to the answer but it did not work so here is the solution I used, as suggested the answer was to send the data from the controller to the model (Although the answers left out using the view to call the controller method) here is my solution
Model - models/awizard.rb
class Awizard
include ActiveModel::Validations
cattr_accessor :valid_data
validate :data_validation :if => lambda { |o| o.current_step == "step1" }
def data_validation
if self.valid_data == false || self.valid_data.blank?
errors.add(:valid_data, "not found")
end
end
#Other wizard stuff
end
View - awizard/_step1.html.erb
<div class="field">
<% f.label "valid data? %>
<% #_controller.valid_data %> #Call controller method to send data to model
</div>
Controller
class AwizardController < ApplicationController
def valid_data
data = #data from elsewhere
if !data.blank?
Awizard.valid_data = true
else
Awizard.valid_data = false
end
end
Related
I recently had a rails model that had several callbacks on it like so:
class Model < ActiveRecord::Base
before_validation :fetch_posts
after_create :build_posts
def fetch_posts
fetch_collection
rescue MyException => e
self.errors.add(:post, e.message)
end
def build_posts
fetch_collection.each do |item|
DifferentModel.build(item)
end
end
def fetch_collection
#collection ||= method_that_fetches_collection_from_external_source
end
end
This was working just fine but it was making it extremely difficult to write tests, as whenever I wanted to create a Model I had to stub out all the callbacks. Enter service objects:
class ModelFetcher
attr_reader :model
def initialize(model)
#model = model
end
def save
model.fetch_posts
if model.save
model.build_posts
return true
else
return false
end
end
end
The problem I'm seeing now, in the case where a model does indeed contain an error (from the fetch posts method), it doesn't get carried over to the model.save call in the SO. That is to say, the Model.new has an error, but once I call .save on that Model.new it doesn't maintain the error and the model saves properly.
I considered adding validate :fetch_posts but then I am back in the same situation I was before as this is essentially a callback.
Any advice on how to structure this better? Is it possible to maintain an error from Model.new to .save? Am I fundamentally misunderstanding something?
Thanks!
Here is an alternate solution which is to overwrite run_validations! since you have none.
class Model < ActiveRecord::Base
after_create :build_posts
def fetch_posts
fetch_collection
rescue MyException => e
self.errors.add(:post, e.message)
end
def build_posts
fetch_collection.each do |item|
DifferentModel.build(item)
end
end
def fetch_collection
#collection ||= method_that_fetches_collection_from_external_source
end
private
def run_validations!
fetch_posts
errors.empty?
end
end
Usually this method looks like
def run_validations!
run_callbacks :validate
errors.empty?
end
but since you have no validations it should serve a similar purpose on #save.
Or as I suggested in a comment you can replace save with model.errors.any? Since save will clear your original errors set by fetch_posts but errors.any? Will check if there were errors during the fecth_posts method.
In my Rails app there is a view with a simple user form consisting of a text box and a submit button.
When the user submits the form, depending on his input, different models are created:
class MessageController < ApplicationController
def create
if is_foo params[:text]
Foo.create
else
Bar.create
end
end
def is_foo(text)
# Here the message gets parsed
# i.e if text[0] == "M"
end
end
My question is, do you think that it's a better design to put the "is_foo" logic inside the Foo model instead of the controller like so?
Model:
class Foo < ActiveRecord::Base
def self.is_foo(text)
# Here the message gets parsed
# i.e if text[0] == "M"
end
end
Controller:
class MessageController < ApplicationController
def create
if Foo.is_foo params[:text]
Foo.create
else
Bar.create
end
end
end
On one hand, the model should take care of the logic. On the other, this isn't really logic, its more of an input rule... What do you think guys?
Helper
I'd leave the is_foo out of the model, as model logic should be to do with the model directly, not determining which model should be created / saved
I would personally look at using a helper method for the test - calling the file ControllerHelper or similar:
#app/helpers/controller_helper.rb
class ControllerHelper
def is_foo? text
# Here the message gets parsed
# i.e if text[0] == "M"
end
end
This will allow you to call the helper in your controller, giving you the ability to use the logic to form the fixes:
#app/controllers/messages_controller.rb
class MessagesController < ApplicationController
include ControllerHelper
def create
model = is_foo?(params[:text]) ? "foo" : "bar"
model.constantize.send(:create)
end
end
I wouldn't call it a ControllerHelper module as mentioned in Rich Pecks answer (since helpers in Rails are view-related), but something like
# app/lib/foo_bar_creator.rb
FooBarCreator = Struct.new(:params) do
def create
build.save
end
def build
klass.new
end
def is_foo?
params[:text] == 'foo'
end
def klass
is_foo? ? Foo : Bar
end
end
(some call these kind of classes "Service Objects")
This way I could just call FooBarCreator.new(params).create in my controller.
I know this sounds like a ridiculous question but I trying to solve a chalange given by an potential employer. I have a schema and a couple of models with their methods. Almost all the methods have no variables passed in. Meaning none of the methods look like this:
def this_is_my_method(variable)
#stuff
end
or
def this_is_my_method variable
#stuff
end
but there are methods that are clearly working with variables like this:
def build_address
if variable
# do something
end
end
Is there a RoR way that a model method will just know about certain parameters or variables in certain situations?
So if my controller was recieving params that looked like this:
?my_method[begin]=1&my_method[end]=5
would the model method "my_method" know what "begin" and "end" where?
def my_method
if self.begin == self.end
# do something
else
# do something else
end
end
Remember that a model method has access to all the attributes (and other methods) of that model instance.
So (for example) this would be a valid model method.
class User < ActiveRecord::Base
def full_name
[first_name, last_name].join(' ')
end
end
This is taking an attribute user.first_name and an attribute user.last_name and combining them to create a new method user.full_name
EDIT as #Sanket has suggested you can pass values into a model if you make them attribute accessor...
def SomeController < ApplicationController
def some_controller_method
#user = User.find(params[:id])
#user.begin = params[:begin]
#user.end = params[:end]
#user.some_model_method
end
end
def User < ActiveRecord::Base
attr_accessor :begin, :end
def some_model_method
if self.begin == self.end
# do something
else
# do something else
end
end
end
Although to be frank I'd rather just pass the values in as method arguments.
Currently I am using the Last.fm api to return concert data (returns a hash) in my controller, and in the view cycling through this hash to return the data I want. I want this concert data to become more dynamic and put everything into a model. How do I do this? Should I do this in the controller or somehow in the model?
Here is an example of my code
# app/controllers/events_controller.rb
class EventsController < ApplicationController
def index
#events = #lastfm.geo.get_events("Chicago",0,5)
respond_with #events
end
end
# app/views/events/index.html.erb
<% #events.each do |event| %>
Headliner: <%= event["artists"]["headliner"] %>
<% end %>
In this example I would would want and Event Model with headliner as a parameter, and put all 5 of the events into this model.
I believe it's a good idea to have a model. There are several advantages as I can see
1 - You could access data as OO way as other objects
2 - if you have some business logics (Ex: calculations) you could do it in the model itself with out messing up your view
3 - it's clean and DRY
Example model class would be (this is not a working model, but just to give you an idea):
class Event
attr_accessor :headliner
def self.event_list(limit = 5)
lastfm.geo.get_events("Chicago",0,limit)
end
end
So you can clean-up your view as
<% Event.each do |event| %>
Headliner: event.headliner
<% end %>
It's difficult to thoroughly answer this question without more knowledge about the last.fm API. As a general rule, you want to keep most of your complex logic and relationship data in the model.
For example, you already know you need an Event model, but it also looks like you might need an Artist model as well. You might end up with something like this:
# app/models/artist.rb
class Artist
attr_accessor :name
def initialize(name)
self.name = name
end
end
# app/models/event.rb
class Event
attr_accessor :artists
def initialize(attributes)
#attributes = attributes
self.artists = attributes['artists'].map do |artist_name|
Artist.new(artist_name)
end
end
def headliner
#headliner ||= self.artists.detect do |artist|
#attributes['headliner'] == artist.name
end
end
end
# app/controllers/events_controller.rb
class EventsController < ApplicationController
def index
#events = #lastfm.geo.get_events('Chicago', 0, 5).map do |event_attributes|
Event.new(event_attributes)
end
respond_with #events
end
end
You might also want to look into ActiveModel, which has some helpful features for models that aren't database-backed and can't inherit from ActiveRecord::Base.
I have this code in my every model.
Class people
def before_validation
#attributes.each do |key,value|
self[key] = nil if value.blank?
end
end
end
Now i want to put my loop in separate module. Like
Module test
def before_validation
#attributes.each do |key,value|
self[key] = nil if value.blank?
end
end
end
And i want to call this before_validation this way
Class people
include test
def before_validation
super
.....Here is my other logic part.....
end
end
Are there any way to do it like that in rails??
You can setup multiple methods to be called by the before_validation callback. So instead of straight up defining the before_validation, you can pass the methods you want to get called before validation.
module Test
def some_test_before_validaiton_method
# do something
end
end
class People < ActiveRecord::Base
include Test
def people_before_validation_foo
#do something else
end
before_validation :some_test_before_validation_method
before_validation :people_before_validaiton_foo
end
You can read more about callbacks here: http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html