How to validate user input in RoR?

Question

I really don't know advice with validating user input. I'm begining with RoR. I read many pages about this issues, but I never get, what I want. Before RoR, I programmed in Java. My problem is: How I can do validate empty field and show error messages? Here are code fragments:

polls_controller.rb

class PollsController < ApplicationController

 def create

  @poll = Polls.new
  @poll.question = params[:question]
  @poll.author_ip = request.remote_ip

 end

 def show
 end

 def new
 end

 def edit
 end

end

polls.rb

class Polls < ActiveRecord::Base
  has_many :options
  validates_presence_of :question, :message => 'Something is wrong...'
end

create.html.erb

<p>
 <% form_tag polls_path do %>

  <%= label_tag :question, "Enter your question:" %><br>
  <%=text_field_tag :question, params[:question] %>
  <%=submit_tag "Send"  %>

 <% end %>
</p>

Answer 1

First, don't add meaningless messages to validations, default error messages are good.

Second, change your code to something like this in controller:

def new
  @pool = Pool.new
end
def create
  @pool = Pool.new(params[:pool])
  if @pool.save
    flash[:notice] = "Some text indicating it was created"
    redirect_to pool_path(@pool)
  else
    flass[:error] = "Somethig is wrong"
    render :new
  end
end

and view use form helper:

<% form_for @pool do |f| %>
  <%= f.error_messages %>
  <%= f.label :question, "Enter your question:" %><br>
  <%= f.text_field :question %><br>
  <%= submit_tag "Send" $>
<% end %>

This way you have validation in mode, and in controller you only need to check if model can be saved. It not, then in your view form can display error_messages for that model.

For displaying flash messages in layout place:

<% if flash[:notice] -%>
  <p class="notice"><%= flash[:notice] %></p>
<% end -%>
<% if flash[:error] -%>
  <p class="error"><%= flash[:error] %></p>
<% end -%>

Answer 2

Include

<% if flash[:notice] %> <%= flash[:notice] %> <% end %>

somewhere in your web page, but preferably in app/views/layouts/application.html.erb.

Refer to RoR tutorials for more info.

Answer 3

I'd check out this post, for one thing. ActiveForm can help quite a bit here. However, if you want to roll this yourself you could easily add some validation in the controller as the poster here did in his updated version of the code.

def results
if params[:name] && !params[:name].blank?
 @name = params[:name]
else
 raise MyApp::MissingFieldError
end

if params[:age] && !params[:age].blank? && params[:age].numeric?
  @age = params[:age].to_i
else
  raise MyApp::MissingFieldError
end
rescue MyApp::MissingFieldError => err
 flash[:error] = "Invalid form submission: #{err.clean_message}"
 redirect_to :action => 'index'
end

Then you just need to display the flash[:errors] in your .erb if it exists.

I'd also have a look at something like this.