Rails form_for that uses STI base class - ruby-on-rails

I've got a pretty simple (I think) single-table inheritance (STI) setup in my Rails app.
There is a User model with a nested resource Post.
Using STI, I have it so that some Posts can be Post::Urgent objects.
I noticed that my URL helpers like <%= [#user, #post] %> needed to be hard-coded to <%= user_post_path[#user, #post] %> or else I'd end up seeing errors about Rails not finding the user_post_urgent_path method. Okay, that was reasonably easy.
(An alternate way of doing this is also <%= [#user, post: #post] %>.)
Well, for some reason I'm not able to figure out how to make the form_for method adjusted in the same way. When I write simply
<%= form_for [#user, #post] do |f| %>
, I get similar errors to the URL helper case, but in the form context: undefined method 'user_post_urgen_path'.
I fixed this by specifying:
<%= form_for [#user, #post], url: :user_post do |f| %>
But this doesn't completely work, because when I go to submit the form, I get problems in my controller, saying that strong parameters line params.require(:post) failed:
param is missing or the value is empty: post
If I inspect the params I find that the form is passing a post_urgent object and not a post object.
I could, of course, manually put in some logic that always says if !params[:post] and params[:post_urgent], then params[:post] = params[:post_urgent]. But that just seems way too hacky, especially for Rails.
Is there a better way to make a form like this "just work" regardless of what subclass of the Post model it actually happens to be?

Not sure if you found a solution already, but I am using the following for my forms
= form_for [#user, #post.becomes(Post)] do |f|
- f.object = #post.becomes #post.class
reference: http://thepugautomatic.com/2012/08/rails-sti-and-form-for/

I had some nested models initialized in the controller, empty unsaved models to work with accepts_nested_attribues_for and becomes empties them for some reason, so instead, I acted on the controller strong params, not the cleanest, I know.
def unpermitted_model_params
polymorphic_form_params = params.to_unsafe_hash
.slice('sub_model1', 'sub_model2')
form_values = polymorphic_form_params.first.to_a.second
ActionController::Parameters.new(parent_model: form_values)
end
def allowed_params
unpermitted_model_params.require(:parent_model)
.permit(:type, :etc, :etc)
end

Related

matching POST route rails 4

I am trying to upload a photo but after I press the upload button, I get this error. I am new to rails 4 so I'm not sure what I am missing.
My logic is when I click the submit button. This will cause the create action to fire and create a IncomePicture object and store it in my database.
No route matches [POST] "/income_pictures/new"
Routes:
root_path GET / static_pages#home
income_pictures_path GET /income_pictures(.:format) income_pictures#index
POST /income_pictures(.:format) income_pictures#create
new_income_picture_path GET /income_pictures/new(.:format) income_pictures#new
edit_income_picture_path GET /income_pictures/:id/edit(.:format) income_pictures#edit
income_picture_path GET /income_pictures/:id(.:format) income_pictures#show
PATCH /income_pictures/:id(.:format) income_pictures#update
PUT /income_pictures/:id(.:format) income_pictures#update
DELETE /income_pictures/:id(.:format) income_pictures#destroy
Controller:
class IncomePicturesController < ApplicationController
def new
#income_picture = IncomePicture.new
end
def create
#income_picture = IncomePicture.new(IncomePicture_params)
if #income_picture.save
flash[:notice] = "Income picture successfully uploaded"
redirect_to #income_picture
end
end
def show
#income_picture = IncomePicture.find(params[:id])
end
def index
#income_picture = IncomePicture.all
end
private
def IncomePicture_params
params.require(:income_picture).permit(:image, :name)
end
end
View:
<%= form_for :income_picture, :html => { :multipart => true } do |f| %>
<p>
<%= f.label :name %>
<%= f.text_field :name %>
</p>
<p>
<%= f.label :image %>
<%= f.file_field :image %>
</p>
<p><%= f.submit %></p>
<% end %>
I think you want form_for #income_picture rather than form_for :income_picture.
From the form guide: Using a symbol creates a form to new_income_picture_path, i.e. /income_picture/new whereas using a populated instance variable creates a form to income_pictures_path, i.e. income/pictures. Both set the form's method to POST. However, there's no such route as POSTing to /income_picture/new/, which is what caused the error.
form_for
To elaborate on the accepted answer, you have to remember that when calling form_for, Rails does some pretty amazing things:
It takes an ActiveRecord object and builds a "route" out of it (from the model)
It populates the form with the ActiveRecord object's data
It allows you to retain a perceived persistent state on the form (by perpetuating the data)
The problem you have is you're passing a simple symbol to the form - which prevents Rails from being able to accurately access the data required to make the 3 "magic" steps above possible.
This means you'll get random errors like the one you're seeing (IE in the absence of an ActiveRecord object, Rails will just use the same URL that you have on your page - /new)
--
ActiveRecord
The way to fix the issue you have is to replace the symbol with an ActiveRecord object, which was suggested in the accepted answer.
The reason why using an ActiveRecord object (#instance_variable) works is because of Ruby's core functionality -- it's a object orientated language. Being object orientated, it means that each time you populate an ActiveRecord object, you'll basically give Rails a series of other information, such as model_name etc.
This means when you pass the #instance_variable to the form_for method, Rails will be able to take the data from ActiveRecord & process it on screen for you

Why is my Rails form helper written improperly?

I know I've written it wrong, but I'm looking at the documentation and can't figure out how.
My model is Quote and has three fields, body, attribution, and work, all strings. The form is intended to add a new quote to a page of quotations.
on main/index.html.erb
<%= form_for(:quote, url: {action: 'create'}) do |f| %>
<%= f.text_field :body %>
<%= f.text_field :attribution %>
<%= f.text_field :work %>
<%= submit_tag "Submit" %>
<% end %>
in main_controller.rb
def create
Quote.create(body: params[:body], attribution: params[:attribution], work: params[:work])
end
The form submits, and an entry is saved to the database -- but it's a totally blank entry. I'm not sure why. Help would be appreciated!
Three things:
The way rails forms are supposed to work, you're not meant to get body, attribution, etc independently, they should be wrapped up into a quote object. But...
In your form, your not properly binding an object to the form the way rails expects. You can read more in the documentation here: http://guides.rubyonrails.org/form_helpers.html#binding-a-form-to-an-object. You could also generate a fake scaffold rails generate scaffold HighScore game:string score:integer to generate a fake model and see an example of how it's supposed to work. The default scaffolding even has simple examples of how to deal with save errors.
Finally, as #Paven suggested, when you get confused, be sure to look at what's going on in your log - i.e. what params are being posted to your create action. That is always helpful and a good way to diagnose problems quickly.
Your form does't need the action argument. The form_for helper uses ActiveRecord objects to determine the path, meaning as long as you build your object correctly, you won't need to determine your path individually:
<%= form_for #quote do |f| %>
Secondly, you'll want to look at your create method:
#app/controllers/quotes_controller.rb
def new
#quote = Quote.new
end
def create
#quote = Quote.new(quote_params)
end
private
def quote_params
params.require(:quote).permit(:body, :attribution, :work)
end
The problem is you're not sending an ActiveRecord object to your form_for helper. You can read the explanation here:
In Rails, this is usually achieved by creating the form using form_for
and a number of related helper methods. form_for generates an
appropriate form tag and yields a form builder object that knows the
model the form is about. Input fields are created by calling methods
defined on the form builder, which means they are able to generate the
appropriate names and default values corresponding to the model
attributes, as well as convenient IDs, etc. Conventions in the
generated field names allow controllers to receive form data nicely
structured in params with no effort on your side.
In order to get the form working correctly, you need to be able to provide a valid ActiveRecord object (#variable), which the helper can use to determine the url etc
My code above helps you provide a new ActiveRecord variable, and allows you to use it in the form. This should allow the form_for method to send your data to the create method, which will then create & save an object in the db for you

how form_for works in Ruby on Rails

I am an newbie. I have read the API documentation. But still don't understand how form_for works.
Firstly, from Ruby on Rails Tutorial, the form for follow button:
<%= form_for(current_user.relationships.build(followed_id: #user.id)) do |f| %>
<div><%= f.hidden_field :followed_id %></div>
<%= f.submit "Follow", class: "btn btn-large btn-primary" %>
<% end %>
I understand current_user.relationships.build(followed_id: #user.id) means a new record. But why can we not just submit and trigger controller to save the record without hidden_field? Why do we still need to post followed_id to controller?
Secondly, in hidden_field, what does :followed_id means? I believe that is a symbol, i.e. it equals only "followed_id" not a variable of id. If that is only the name of the input field, then what is its value?
Thirdly, how does form_for know where the submission should be sent to? Which controller and action the form_for will post to?
Fourth, how does params work with form_for? In this follow button case, params[:relationship][:followed_id] will return #user.id in controller. How does it know the first hash attribute is :relationship? We have neither mentioned form_for :relationship nor form_for #relationship.
I know these questions can be very dumb, but I am really stuck. Any help will be appreciated.
I didnt do that tutorial so mind me if i dont answer directly to your question.
Take a look at the rails guide about form helpers and it explains in details your questions, probably in a more articulate way than i can.
form_for(path/to/your/controller/action) is a helper method to create HTML form elements with the url path to the POST or GET request. The helper knows if it should be a new record or an update record based on what you are asking to do in your controller action.
For example
In your controller
def new
#my_instance_variable = Myobject.new
end
In your view new.html.erb
<%= form_for #my_instance_variable do |f| %>
...
<% end %>
In your case the logic was directly written in the helper and you could also directly write
<%= form_for Myobject.new %>
Both will result with the following html
<form action="/myobjects/new" method="post">
# in this case rails knows its a `POST` request because the route new action
# is by default a POST request. You can check these routes and their request
# by using `rake routes` in terminal.
Then the hidden_field is another helper to contain a value, in your case the #user.id that will be passed as parameter then saved as a Create or update action for the given object. The reason it doesnt add the value in the hidden field tag is because you already have a model association that knows the id of user since the link of form uses the build method with user id.
Last part you need to understand the form_for link logic
current_user.relationships
# implies the association of the current_user has many relationships
current_user.relationships.build
# .build is a method to populate a new object that can be save as a new record
# means you will create a new relationship record by populating the user_id
# column with the current_user.id and the followed_id with the target #user.id
After reading the book The Rails 4 Way, I understand form_for better now.
11.9.1.5 Displaying Existing Values.
If you were editing an existing instance of Person, that object’s attribute values would have been filled into
the form.
in this way, when we build the relationship by usingcurrent_user.relationships.build(followed_id: #user.id), the relationship instance will be created and gain attribute followed_id. So that, instead of "creating" a relationship, we are actually editing the relationship by the form.
Then Rails will know you are editing and load the existing attribute "followed_id" to the field. Therefore, we don't need to assign value to the field like using f.hidden_field :followed_id, value: #user.id.
And the reason why we have to use a field to pass followed_id to params is because HTTP server is stateless, it doesn't remember you are creating a relationship with which user.
One of the advantages of writing form_for current_user.relationships.build(followed_id: #user.id) instead of standard form_for #relationship is we don't need to write "if-condition" in controller like this:
unless current_user.nil?
if current_user.following?(#user)
#relationship=current_user.relationships.find_by(followed_id: #user.id)
else
#relationship=current_user.relationships.new
end
end
params will be sent to the controller which belongs to the instance's model. "post" method will go to action create, "delete" will go to destroy, "patch" will go to update, etc.
params will be a hash with another hash inside like { instace_name: { field_1: value1, field_2:value2 } } or full params as below
Parameters: {"utf8"=>"✓",
"authenticity_token"=>"afl+6u3J/2meoHtve69q+tD9gPc3/QUsHCqPh85Z4WU=",
"person"=>{"first_name"=>"William", "last_name"=>"Smith"},
"commit"=>"Create"}

ArgumentError in Rails

I want to connect two entity (project and issues) and Rails says some error message, but I don't know, what should I do. Can you help me fix it, please? Thanks a lot.
Not sure what your are trying to do, but it looks like you have a nested resource and therefore want to pass an array to form_for, but you are actually passing two separate objects. Change:
<%= form_for(#project, #project.issues.build) do |f| %>
to:
<%= form_for([#project, #project.issues.build]) do |f| %>
With this change you'll pass one array for form_for, instead of two arguments.
I think you have used nested resources like this:
resources projects do
resources issues
end
If you used that, try make your form like this:
<%= form_for([#project, #issue]) do |f| %>
and in your IssueController :
def new
#project = Project.new
#issue = #project.issues.build(params[:issue])
end
def create
#project = Project.find(params[:project_id]
#issue = #project.issues.create(params[:issue]
end
and run again to see something happen. Hope this help.

How can you pass an object from the form_for helper to a method?

So let's say I have a form which is being sent somewhere strange (and by strange we mean, NOT the default route:
<% form_for #form_object, :url => {:controller => 'application',
:action => 'form_action_thing'} do |f| %>
<%= f.text_field :email %>
<%= submit_tag 'Login' %>
<% end %>
Now let's say that we have the method that accepts it.
def form_action_thing
User.find(????? :email ?????)
end
My questions are thus:
How can I make the object #form_object available to the receiving method (in this case, form_action_tag)?
I've tried params[:form_object], and I've scoured this site and the API, which I have to post below because SO doesn't believe I'm not a spammer (I'm a new member), as well as Googled as many permutations of this idea as I could think of. Nothing. Sorry if I missed something, i'm really trying.
How do I address the object, once I've made it accessible to the method? Not params[:form_object], I'm guessing.
EDIT
Thanks so much for the responses, guys! I really appreciate it. I learned my lesson, which is that you shouldn't deep-copy an object from a form, and that the parameters of a form are actually included when you submit it.
I will admit it's sort of disheartening to not know stuff that seems so obvious though...
you need to pass the "id" of your "#form_object" in the url and then lookup that object (assuming you have a model and using ActiveRecord)
It depends on how do you set up your routes. If you're using the default /:controller/:action/:id route, you can pass it as a parameter in the URL. Note that not the whole #form_object can/should be passed, but it's id or some other attribute to identify it instead. In this case, you should make your URL:
<% form_for #form_object, :url => {:controller => 'application',
:action => 'form_action_thing', :email => some_email} do |f| %>
<%= f.text_field :email %>
<%= submit_tag 'Login' %>
<% end %>
And in your controller
def form_action_thing
#user = User.find_by_email(params[:email])
end
You can pass parameters through the url, but when submitting a form the only thing that should (probably) be passed through the url is the record id for a RESTful record.
And it appears you didn't find out yet where your form data can be found in the params.
So
All the data from your form should end up in params[:form_object]. The actual value for :form_object is selected by Rails, it's probably coming from the object's class (too lazy to look that up right now)
In any case, you can easily find out where your form values are submitted by looking at your console/log output. All the params for each requests are dumped there.
The form fields will be inside the params like params[:form_object][:email] - each field that is submitted has an entry corresponding to the field name.
The params hash not contain all the original values from your #form_object. There will be only those values that you included in the form.
If you need to pass non-editable values to the controller with your form, use hidden_field(s) These will be submitted with the form, but are not visible to the user.

Resources