Railscasts - Complex Forms Part 3

#75

Oct 15, 2007

Complex Forms Part 3

In this third and final episode on complex forms I will show you how to edit a project and multiple tasks all in one form. This includes removing and adding tasks dynamically as well. See the show notes for updated code.

Tags: forms views models ajax

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Resources

Update (3/29/2008)

The code for this screencast isn’t the greatest, it requires the :index option for the fields and does not work well in Rails 2. Instead I recommend going with the approach I show in Advanced Rails Recipes. Here’s the code (posted by permission). Check out the recipe for details on how it works.

If you want, you can also view the original code.

<!-- projects/edit.rhtml -->
<% form_for :project, :url => project_path(@project), :html => { :method => 'put' } do |f| %>
  <%= render :partial => 'fields', :locals => { :f => f } %>
  <p><%= submit_tag "Update Project" %></p>
<% end %>

<!-- projects/new.rhtml -->
<% form_for :project, :url => projects_path do |f| %>
  <%= render :partial => 'fields', :locals => { :f => f } %>
  <p><%= submit_tag "Create Project" %></p>
<% end %>

<!-- projects/_fields.rhtml -->
<p>
  Name: <%= f.text_field :name %>
</p>
<div id="tasks">
  <%= render :partial => 'task', :collection => @project.tasks %>
</div>
<p><%= add_task_link "Add a task" %></p>


<!-- projects/_task.rhtml -->
<div class="task">
  <% fields_for_task(task) do |task_form| %>
  <p>
    Task: <%= task_form.text_field :name %>
    <%= link_to_function "remove", "$(this).up('.task').remove()" %>
  </p>
  <% end %>
</div>

# models/project.rb
class Project < ActiveRecord::Base
  has_many :tasks, :dependent => :destroy

  validates_presence_of :name
  validates_associated :tasks
  
  after_update :save_tasks

  def new_task_attributes=(task_attributes)
    task_attributes.each do |attributes|
      tasks.build(attributes)
    end
  end
  
  def existing_task_attributes=(task_attributes)
    tasks.reject(&:new_record?).each do |task|
      attributes = task_attributes[task.id.to_s]
      if attributes
        task.attributes = attributes
      else
        tasks.delete(task)
      end
    end
  end
  
  def save_tasks
    tasks.each do |task|
      task.save(false)
    end
  end
end


# models/task.rb
class Task < ActiveRecord::Base
  belongs_to :project
  validates_presence_of :name
end


# projects_controller.rb
def new
  @project = Project.new
  @project.tasks.build
end

def create
  @project = Project.new(params[:project])
  if @project.save
    flash[:notice] = "Successfully created project and tasks."
    redirect_to projects_path
  else
    render :action => 'new'
  end
end

def edit
  @project = Project.find(params[:id])
end

def update
  params[:project][:existing_task_attributes] ||= {}
  
  @project = Project.find(params[:id])
  if @project.update_attributes(params[:project])
    flash[:notice] = "Successfully updated project and tasks."
    redirect_to project_path(@project)
  else
    render :action => 'edit'
  end
end


# projects_helper.rb
def fields_for_task(task, &block)
  prefix = task.new_record? ? 'new' : 'existing'
  fields_for("project[#{prefix}_task_attributes][]", task, &block)
end

def add_task_link(name) 
  link_to_function name do |page| 
    page.insert_html :bottom, :tasks, :partial => 'task', :object => Task.new 
  end 
end

Validation

Displaying the validation errors can be tricky depending on your needs. It may be as simple as displaying the project validations:

<!-- projects/_fields.rhtml -->
<%= error_messages_for :project %>

This will mention if there are task validation errors, however it will not state exactly what the errors are because these are stored in each task model.

If you need to display the task error messages. One way is to do this:

<!-- projects/_task.rhtml -->
<% @task = task %>
<%= error_messages_for :task %>

The error_messages_for method requires an instance variable with the same name, so that is why it needs to be set right there. This is an ugly work around. If you want to do it in a cleaner way or handle the error messages differently then I recommend creating your own validation helper method instead. I may go into more details in a future episode.

If you want to share your validation troubles feel free to add a comment!

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241 comments

1. Jorge Calás Oct 15, 2007 at 01:54

Great! As always.

Thanks very much for sharing all this, helping us to be better programmers.

Watching your screencast has become my every monday's firt task ;)

Complex Forms Part 3

Update (3/29/2008)

Validation

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