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How do I pass local variables to iteration in turbo_stream?

Gabriel asked in Ruby

In my app I have projects which have many tasks. The tasks are iterated through on the projects show page:

### Project#show 

 <% @tasks.each do |task| %>
    <tr class="cursor-pointer">
       <td class="px-6 pr-3 py-4 w-12">

         <%= form_with(...) do |form| %>
           <div id="task_checkbox_<%= %>">
              <%= render partial: "projects/partials/task_checkbox", locals: { form: form, task: task } %>
         <% end %>

<% end %>

The Partial however has the regarding form element which is a radio button:

### Partial: projects/partials/_task_checkbox.html.erb

<%= form.label :done, value: false, class:"block whitespace-nowrap" do %>
<%= form.radio_button(:done, false, class:"hidden", onchange: "this.form.requestSubmit()") %>
  <p>Radio Button Label</p>
<% end %>

If i click the radio button within the iteration for tasks, the task switches it's state to done: true as expected. However the whole thing is tied to a turbo_stream:

### update.turbo_stream.erb -> Update action of tasks_controller

<%= turbo_stream.replace "task_checkbox" do %>
<%= render partial: "projects/partials/task_checkbox", locals: { form: form, task: task } %>
<% end %>
### tasks_controller.rb

 def update
    respond_to do |format|
      if @task.update(task_params)
        format.html { redirect_to task_url(@task), notice: "Task was successfully updated." }
        format.json { render :show, status: :ok, location: @task }
        format.html { render :edit, status: :unprocessable_entity }
        format.json { render json: @task.errors, status: :unprocessable_entity }

Since the partial is within the tasks iteration and a form, i pass two local variables form and task. However, updating the task to done: true returns an error for the turbo_stream unit as follows:

undefined local variable or method 'task'

I found this file within the turbo-rails rep (, which does not really help me, since the use case is different (i font want to replace the whole iteration but one field). Variations didn't work either so far.

How do I pass local variables through a turbo stream to a partial?

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