Question

I have made a resource.

resources :dashboards

I have a partial file which contains a form and I want to use this partial (as the form elements won’t change) to update and create. So here is what I have:

Controller

class DashboardsController < ApplicationController
 def new     
    @dashboard = Dashboard.new
  end
end

View

/dashboards/new.html.erb

<%= render :partial => "form", :locals => { :dashboard => @dashboard } %>

Partial Form

/dashboards/_form.html.erb

<%= form_for(@dashboard) do |form| %>
.....
<% end %>

Ruby Guide

The Ruby Guide states:

The Article model is directly available to users of the application, so — following the best practices for developing with Rails — you should declare it a resource. When dealing with RESTful resources, calls to form_for can get significantly easier if you rely on record identification. In short, you can just pass the model instance and have Rails figure out model name and the rest. For example:

## Creating a new article
# long-style:
form_for(@article, :url => articles_path)
# same thing, short-style (record identification gets used):
form_for(@article)

## Editing an existing article
# long-style:
form_for(@article, :url => article_path(@article), :html => { :method => "put" })
# short-style:
form_for(@article)

Result

I thought I have followed the Rails Guide correctly. Because I made @dashboard a resource. I could just pass it into the form and have it handle the action, method and the rest. Instead I’m getting this:

<form accept-charset="UTF-8" action="/dashboards" class="new_dashboard" id="new_dashboard_" method="post">

According to the docs. Shouldn’t the action of my form now be “/dashboards/new” because we are on the new action? And should it be passing an extra field declaring the method to be put when I use the same code in the /edit action??

My result is always the same no matter what. The form never changes.

What am I doing wrong?

EDIT

Here is my router info from rake routes

GET    /dashboards(.:format)          dashboards#index
POST   /dashboards(.:format)          dashboards#create
GET    /dashboards/new(.:format)      dashboards#new
GET    /dashboards/:id/edit(.:format) dashboards#edit
GET    /dashboards/:id(.:format)      dashboards#show
PUT    /dashboards/:id(.:format)      dashboards#update
DELETE /dashboards/:id(.:format)      dashboards#destroy

Answer 1

You are correct that you should be able to “pass @dashboard into the form and have it handle the action, method and the rest.” The issue here is what new is in the context of RESTful actions.

When you declare a set of resources with resources :dashboards, you are creating a set of routes which map requests to controller actions:

GET     /dashboards             index
GET     /dashboards/new         new
POST    /dashboards             create
GET     /dashboards/:id         show
GET     /dashboards/:id/edit    edit
PUT     /dashboards/:id         update
DELETE  /dashboards/:id         destroy

You can check this if you run rake routes.

The issue here is that the new action is defined as a GET request to the path /dashboards/new, i.e. this is the route for the form itself. The URL in the action attribute of the actual form is something else: this is where the form will post the data to with a POST request, which on the server (rails) side will map to the create controller action.

When you use the form helper with form_for(dashboard), a form is created with a route corresponding to what dashboard is: if it is a new record (i.e. it does not yet exist in the database), then the form action will be create (and point to /dashboards), whereas if it already exists it will point to the actual URL for the record (e.g. /dashboards/123). This is what makes the form helpers so useful.

So, to sum up, /dashboards is the correct URL, not for the new action but for the create action, which the form helper uses because dashboard is a new record. new is the route to the page where the form resides, i.e. /dashboards/new.

Hope that makes sense.

p.s. as a side note, you shouldn’t be accessing @dashboard in the partial if you are passing it in as a local (:locals => { :dashboard => @dashboard }). Just use dashboard.