Rails Fundamentals - Validations

Exercise Questions
1

This topic is for the Validations exercise in the Rails Fundamentals trail. Post any questions, corrections, or pointers you have to share with other Upcase subscribers.

2

Trying to do the Validations exercise on the Ruby on Rails trail and I canā€™t workout how to pass the error object back to the welcome controller from the GuestbookEntries controller when the form input is invalid - Iā€™m assuming Iā€™m missing something blindingly obvious but canā€™t work it out. Any suggestions?

1 Like
3

https://exercises.upcase.com/exercises/validations

I remember doing this exercise and thinking that the design was a bit odd.

Hereā€™s a hint: One controller can render views which are for another controller just by calling render with a path. For example render 'widgets/show' will render app/views/widgets/show, even if called from some controller other than WidgetsController.

4

Hmmmā€¦I tried that (doing a render ā€˜pages/welcomeā€™) but was then getting issues as the @guestbook_entries wasnā€™t defined as I define that in the welcome controller which isnā€™t getting called

5

Calling render isnā€™t the same as a redirect. For instance, given the following code you might expect calls to FooController.create to execute the code in PagesController.welcome thereby setting the @guestbook_entries variable. But this isnā€™t actually the case, render simply tells Rails what view content it needs to serve to the browser. If the resulting view template makes use of the @guestbook_entries variable then youā€™ll need to define it once again in the controller action that makes the call to render.

class PagesController < ApplicationController
  def welcome
    @guestbook_entries = ...
  end
end

class FooController < ApplicationController
  def create
    @guestbook_entries = ...
    render 'widgets/show'
  end
end

You also have the option of using redirect_to instead of render, but youā€™ll need to relay the error messages into the flash hash:

def create
  ...
  redirect_to(welcome_index_path, flash: { error: @foo.errors })
end
6

Unless itā€™s been changed recently, the controller spec supplied with the exercise needs the template to be rendered:

describe GuestbookEntriesController do
  describe "#create" do
    context "invalid entry" do
      it "renders the welcome view" do
        post :create, guestbook_entry: { body: "" }
        expect(response).to render_template "pages/welcome"
      end
    end
  end
end
7

Thanks a lot for your help - I did just have to use the render on the welcome/page and then re-declare the guestbook entries within the create to get it to pass. Iā€™m not overly keen on my solution so will go through and look and see how other people have done it to hopefully find a neater solution.

Once again, thank you!

1 Like
8

Set the flash with the errors object See: Layouts and Rendering in Rails ā€” Ruby on Rails Guides

9

I had to rewrite one of the tests. Render test like this are new to me. But I had to set the flash within the test, since apparently the assign() is mocking the controller, and the flash hadnā€™t been set there. Are we expected to not use the flash, and call @guestbookEntry.errors.messages directly in the view?

it "displays the error messages of an invalid form submission" do
    assign(:guestbook_entries, [])
    g = GuestbookEntry.new body: ""
    g.valid?
    flash[:notice] = g.errors.messages
    assign(:guestbook_entry, g)
    render

    expect(rendered).to have_content("Body can't be blank")
  end
10

I am calling the error messages in the view but I am not seeing them displayed.

My view:

<h1>Welcome to My Guestbook</h1>
<br>
<%= image_tag("under_construction.gif") %>

<div id="guestbook-entries">
  <p>Guestbook Entries:</p>
  <ul>
    <% @guestbook_entries.each do |guestbook_entry| %>
      <%= guestbook_entry.created_at.strftime("%b %d %Y:") %>
      <%= guestbook_entry.body %>
    <% end %>
  </ul>
</div>

<%= form_for @guestbook_entry do |f| %>
<% if @guestbook_entry.errors.any? %>    
    <h2><%= pluralize(@guestbook_entry.errors.count, "error") %> prohibited this entry from being saved:</h2>
    <ul>
    <% @guestbook_entry.errors.full_messages.each do |message| %>
      <li><%= message %></li>
    <% end %>
    </ul>
  <% end %>
  
  <%= f.label :body, "Guestbook Entry:" %>
  <%= f.text_area :body %>
  <%= f.submit "Submit" %>
<% end %>

My guestbook_entries_controller:

class GuestbookEntriesController < ApplicationController
  def create
    guestbook_entry = GuestbookEntry.create(guestbook_entry_params)

    if guestbook_entry.valid?
      redirect_to root_path, notice: "Thank you for your entry."
    else
      @guestbook_entry = GuestbookEntry.new
      @guestbook_entries = GuestbookEntry.all
      render template: "pages/welcome"
    end
  end

  private

  def guestbook_entry_params
    params.require(:guestbook_entry).permit(:body)
  end
end

My model:

class GuestbookEntry < ActiveRecord::Base
  validates :body, presence: true
  validates :body, length: { maximum: 255 }
end
11

When you call guestbook_entry.valid?, that will set errors on the guestbook_entry. However, this is a local variable (no @ prefix)., so it never gets shared with the view.

(I think itā€™s better if I donā€™t spell out the solution, hopefully this will get you on the right track!).