Create and show items in the samve view

While trying to build a form to create new items on an index page rather than the new view, i ran into a curious problem.

When presenting the form for creation of a new task in the current project, the @tasks variable that contains the tasks that are supposed to be displayed in the list below, seems to be empty. Therefore i get a "No route matches" since the object im passing to ie. complete_project_task_path is nil.

When removing the form, everything works like a charm. Any ideas why this happens?

<h1>Listing tasks</h1>

<%= form_for([@project, @project.tasks.build]) do |f| %>
    <div id="new_quick_task">
        <%= f.text_field :title, :value => 'Quickly add a new task' %>
        <%= f.submit %>
    </div>
<% end %>

<div id="task_list">
    <% @tasks.each do |task| %>

        <div class="task">
            <div class="completed"><%= task.completed %></div>
            <div class="complete_link"><%= link_to "Good", complete_project_task_path(@project, task) %></div>
            <div class="title"><%= link_开发者_运维知识库to task.title, project_task_path(@project, task) %></div>
        </div>
    <% end %>
</div> <!-- end task_list -->

Why do you use @tasks and not @project.tasks? because it would show the new task you created for your form?.

Well, you could still use @project.tasks and do something like:

<% @project.tasks.each do |task| %>
  <% unless task.title.nil? %>
    <div class="task">
        <div class="completed"><%= task.completed %></div>
        <div class="complete_link"><%= link_to "Good", complete_project_task_path(@project, task) %></div>
        <div class="title"><%= link_to task.title, project_task_path(@project, task) %></div>
    </div>
  <% end %>
<% end %>

which would skip the tasks without the title.

The error you get is not because the @tasks variable is empty, because if it was, you would never come to the code below it. The error you get is that one of the items inside your @tasks contains a value it does not expect. I guess it has something to do with your complete_project_task_path(@project, task) that will check something of task that is not set correctly?

So i think i figured it out. (please correct me if im wrong)

Ruby variables hold references to objects and the = operator copies the references.

(from http://ruby-doc.org/docs/Newcomers/ruby.html#objects no. 17)

Taking that into account, look at the following example

@task_list = @project.tasks

This essentially makes @task_list refer to the same object as @project.tasks. If the data in @project.tasks changes, so does @task_list's data because they both point to the same object.

@project.tasks.build seems to alter the object, that both @project.taks and @task_list point to, in some way.

The solution was pretty simple. Instead of setting @task_list = @project.tasks i created a new object for @task_list.

So in the controller, istead of doing this:

@project = Project.find(params[:project_id])
@task_list = @project.tasks

just do it like this:

@project = Project.find(params[:project_id])
@taks_list = Task.where(:project_id => @project.id)