mottigottlieb/rails-edit-update-action-readme-v-000

Edit/Update Action

Rails Controller Conventions

Now that you know how to implement a create action, the next logical step will be to integrate an edit/update action. As you may have noticed, there is a trend in Rails conventions where the logic for rendering a form is separate from the action that manages the database record alteration. For example:

• The new action in the controller simply renders the new form

• The create action is what actually handles the process of inserting the form data into the database

In like fashion, the edit and update actions have a similar convention:

• The edit action will handle rendering the edit form

• The update action will be the method that updates the database record itself

Rendering the edit form

To start off, let's draw a get route for our edit form, since the form will need to know which record is being edited this will need to be a dynamic route that accepts an :id as a parameter so it can be accessed by the controller:

get '/posts/:id/edit', to: 'posts#edit'

We still need to draw one additional route to handle the update action, this route will also need to be dynamic and accept an :id as a parameter so the update action will know what record is being altered. If you're curious on what HTTP verb should be selected, consider that we're sending data to the server, so we know it's not GET, and since we're not creating a new record it shouldn't be POST, so PUT should be the HTTP verb.

put 'posts/:id', to: 'posts#update'

On a side note, as a shortcut you could also simply add the edit and update actions to the resources call in the routes file and that would accomplish the same goal that these two lines do.

If you run rake routes you will see we have two new routes:

Verb    URI Pattern                 Controller#Action
GET     /posts/:id/edit(.:format)    posts#edit
PUT     /posts/:id(.:format)         posts#update

With our routes in place, let's add in the controller actions:

def edit
end

def update
end

And then create the edit view template app/views/posts/edit.html.erb

Let's just copy and paste the form code from the new form:

<h3>Post Form</h3>

<%= form_tag posts_path do %>
  <label>Post title:</label><br>
  <%= text_field_tag :title %><br>

  <label>Post Description</label><br>
  <%= text_area_tag :description %><br>

  <%= hidden_field_tag :authenticity_token, form_authenticity_token %>

  <%= submit_tag "Submit Post" %>
<% end %>

If you open the browser and go to the edit page it will now display the form, but you may have noticed a pretty big flaw, it doesn't load the record's data into the form, there are a few tasks that we'll need to do in order to implement this behavior. First let's have our edit action store the post record in an instance variable:

def edit
  @post = Post.find(params[:id])
end

Now that the edit view template will have access to the @post object, we need to refactor the form so that it auto fills the form fields with the data from the post record. This is done below:

<% # app/views/posts/edit.html.erb %>

<h3>Post Form</h3>

<%= form_tag posts_path do %>
  <label>Post title:</label><br>
  <%= text_field_tag :title, @post.title %><br>

  <label>Post Description</label><br>
  <%= text_area_tag :description, @post.description %><br>

  <%= submit_tag "Submit Post" %>
<% end %>

This will now populate the form, but if you tried to submit the form you may notice that it's redirecting to the show page and not changing the values. Notice how the post_path route helper method is used for the show, update, edit, and delete method? How can we let the app know that we want to use the update method in this case? We need to first make a change to the form so that it knows what route the data should be passed through as well as what HTTP verb needs to be called, make the following change to the form_tag line:

<%= form_tag post_path(@post), method: "put" do %>

By explicitly stating the route and method, the form will now be routed to the update action. Before we try to implement the update action, let's first make sure the data is being routed properly. Enter the following code inside of the update method:

def update
  raise params.inspect
end

The raise method will cause the application to pause and print out the params on an error page. You could also see the params if you called puts params.inspect; using puts would simply require you to track down the data in the rails server log.

If you open up the browser and navigate to an edit page, such as: localhost:3000/post/5/edit, and change some elements in the form and submit it, it should take you to an error page that prints out the params from the form, such as the below image:

As you can see, the parameters are being passed to the update action. With that in mind, let's implement the functionality needed inside of the update action so that it will take the form data and update the specified record. Let's write some pseudo code for what the update action should do:

• Query the database for the Post record that matched the :id passed to the route

• Store the query in an instance variable

• Update the values passed from the form (the update method here is the update method supplied from ActiveRecord, not the update method we're creating). The update method takes a hash of the attributes for the model as its argument, e.g. `Post.find(1).update(title: "I'm Changed", description: "And here too!")

• Save the changes in the database

• Redirect the user to the show page so they can see the updated record

We'll take advantage of the update method so that we're not manually assigning each attribute:

def update
  @post = Post.find(params[:id])
  @post.update(title: params[:title], description: params[:description])
  redirect_to post_path(@post)
end

Now if you go to the edit page and make changes to the title or description form elements you will see they are changed when the form is submitted, so the edit and update functions are working properly!

Extra Credit

• When only one form element is updated, such as the title, does the description also get updated?

• How could we refactor this form code? You may notice that we have a form for the new and edit actions, is there a better way of doing this?

View Edit/Update Action on Learn.co and start learning to code for free.

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View Edit/Update Action on Learn.co and start learning to code for free.