How to pass params to new view in Ruby on Rails app? - ruby-on-rails

Question

I'm trying to make simple app. I input my first name and last name to simple <%= form_for #data do |f| %> rails form and after submitting it, app should render simple text like this. My first name is <%= data.first_name %> and my last name is <%= data.last_name %>. I don't know why but my app is saying this error:
undefined local variable or method `data' for
It's probably saying it because no params are passed to view.
Here is my code.
routes.rb
resources :data, only: [:new, :create, :index]
data_controller.rb
class DataController < ApplicationController
def new
#data = Data.new
end
def index
end
def create
#data = Data.new(data_params)
if #data.valid?
redirect_to #data
else
render :new
end
end
private
def data_params
params.require(:data).permit(:first_name, :second_name)
end
end
/views/data/new.html.erb
<%= form_for #data do |f| %>
<%= f.label :first_name %>
<%= f.text_field :first_name %>
<%= f.label :second_name %>
<%= f.text_field :second_name %>
<%= f.submit 'Continue', class: 'button' %>
<% end %>
/views/data/index.html.erb
<h2>Coolest app ever :D</h2>
<p>My first name is: <%= data.first_name %>.</p>
<p>And my second name is: <%= data.second_name %>.</p>
/models/data.rb
class Data
include ActiveModel::Model
attr_accessor :first_name, :second_name
validates :first_name, :second_name, presence: true
end
Please help to find out why params are not passing to next page. Thanks anyways :D

Answer 1

Your view should look like this:
<h2>Coolest app ever :D</h2>
<p>My first name is: <%= #data.first_name %>.</p>
<p>And my second name is: <%= #data.second_name %>.</p>
Also, I would suggest that calling a model something generic like Data is not a very Rails-y approach. Generally, domain models correspond to real-world things like User and Article, which are easy to understand and relate to. It'll get confusing quite fast if you use need to make another model and want to call it Data2 or something :)

Answer 2

Edit:
Since you specified that you do not wish to use the database, I would recommend passing in the object params through the redirect:
redirect_to(data_path(data: #data))
and in your controller's index method:
def index
#data = Data.new(params[:data])
end
Now your view should render properly, since you're passing the in-memory #data object attributes as params within the redirect. You then recreate this object in the index page or wherever you wish to redirect to.
To expand on Matt's answer, the reason you're getting NilClass errors is because:
You're redirecting to a data#show action when no show action has been enabled within your routes file. Since you've set your views up for the index, I'm assuming you want to redirect there when the #data object has been verified as valid:
redirect_to data_path
However I would recommend you follow Rails conventions and specify the data#show route within your routes.rb:
resources :data, only: [:index, :new, :create, :show]
and in your data_controller.rb:
def show
#data = Data.find(params[:id])
end
Another problem is that you're not actually saving the #data object upon creating it. The new method populates the attributes, and valid? runs all the validations within the specified context of your defined model and returns true if no errors are found, false otherwise. You want to do something like:
def create
#data = Data.new(data_params)
if #data.save
redirect_to data_path
else
render :new
end
end
Using save attempts to save the record to the database, and runs a validation check anyways - if validation fails the save command will return false, the record will not be saved, and the new template will be re-rendered. If it is saved properly, the controller will redirect to the index page, where you can call upon the particular data object you want and display it within your view.