Fixing issue of Rails AJAX causing partials to be overwritten upon page refresh

While trying to implement a user show view with dynamic post creation, I encountered an issue when refreshing the page after successfully creating posts. The issue arises when the previously created posts are overwritten with null IDs. Additionally, I am unsure about the correct placement of the create.js.erb file - should it be in the views folder or the assets/javascripts folder?

Here is an overview of my setup:

UsersController

def show
    @user = User.find(params[:id])
    @posts = Post.all
    @post = @user.posts.build
end

users/show.html.erb

<%= "user-id: #{@user.id}" %>

<ul id="posts">
<%= render :partial => @posts %>
</ul>

<%= form_for(@post, remote: true) do |f| %>
  <%= f.hidden_field :user_id, :value => @user.id %>
  <%= f.submit %>
<% end %>

PostsController

def create
  puts params[:post][:user_id]
  @user = User.find(params[:post][:user_id])
  puts @user
  @post = @user.posts.build()
  respond_to do |format|
    if @post.save
      format.html { redirect_to @post, notice: 'Post was successfully created.' }
      format.js   {}
      format.json { render json: @post, status: :created, location: @post }
    else
      format.html { render action: "new" }
      format.json { render json: @post.errors, status: :unprocessable_entity }
    end
    Rails.logger.info(@post.errors.inspect) 
  end
end

def index
    @posts = Post.all
    @post = Post.new
end

posts/_post.html.erb

 <li><%= @post.id %></li>

posts/create.js.erb

 $("<%= escape_javascript(render @post) %>").appendTo("#posts");

Answer №1

The Issue at Hand

The problem arises from utilizing the instance variable @post instead of the local variable post within your partial, leading to all new posts being rendered.

Within the UsersController#show action, @post = @user.posts.build is set. When rendering <%= @post.id %> inside the partial, it references the same variable set to a new post from the controller.

It may appear as if previously created posts are being nullified, but in reality, a new post is being continuously rendered instead of the existing ones.

The Resolution

To remedy this issue, ensure your partial utilizes a local variable instead of the instance variable.

<li><%= post.id %></li>

Rails automatically provides this local variable when rendering a collection of records like

<%= render @user.posts %>

or alternatively

<%= render partial: "posts/post", collection: @user.posts %>

Preventing Future Occurrences

This is a common mistake that can easily be overlooked. To avoid this, consider eschewing instance variables in partials altogether.

Additional References

Answer №2

Discovered a workaround by omitting the _post partial to showcase the older posts:

update: users/show.html.erb

<ul id="posts">
  <% @posts.each do |post| %>
    <li>
      <%= post.id %>
    </li>
  <% end %>
</ul>

Although not perfect, this solution is effective for the time being.

Answer №3

Absolutely right, your understanding is on point.

Utilize create.js.erb by incorporating the erb extension to seamlessly incorporate Ruby code.

When writing code in this file, follow the same principles as when coding in JavaScript on the html.erb view using appropriate syntax.

<script>
  $("<%= escape_javascript(render @post) %>").appendTo("#posts");
</script>

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