@model OR :model in a form_for

rubyonrails-talk
1

Hi Folks,

I want a form in a rails 3.0.10 app with form_for exactly I have 3 models

@apple, @basket, @table

class Apple     belongs_to :tables     belongs_to: baskets end

class Basket     belongs_to :tables     has_many :apples end

class Table     has_many :baskets     has_many :apples end

MY QUESTION

For apples I have many color as well as for baskets I have many different kinds of shapes

if I have the follow code in the index.html.erb file

<%= form_for :table do |f| %>

<%= f.collection_select(:basket, @basket, :id, :shape, {:prompt => true}) %>

<%= f.collection_select(:apple, @apple, :id, :color, {:prompt => true}) %>

<%= f.submit %>

<% end %>

*** appear the page correctly ***

meanwhile if I have the follow code

<%= form_for @table do |f| %>

<%= f.collection_select(:basket, @basket, :id, :shape, {:prompt => true}) %>

<%= f.collection_select(:apple, @apple, :id, :color, {:prompt => true}) %>

<%= f.submit %>

<% end %>

the page show the follow error page

//////////// undefined method `model_name' for NilClass:Class

Extracted source (around line #1):

1: <%= form_for @table do |f| ////////////

change only the first line in the example I have <%= form_for @table do

f> %> and not

<%= form_for :table do |f| %>

NOW

which is the different between

<%= form_for @table do |f| %>

and

<%= form_for :table do |f| %>

sorry for this post but I want to understand the Rails philosophy

thanks a lot anyway,

C

2

Is it all made with scaffolds? or what do you have in your controller?

Javier Q.

3

Hi Folks,

I want a form in a rails 3.0.10 app with form_for exactly I have 3 models

@apple, @basket, @table

class Apple belongs_to :tables belongs_to: baskets end

class Basket belongs_to :tables has_many :apples end

class Table has_many :baskets has_many :apples end

MY QUESTION

For apples I have many color as well as for baskets I have many different kinds of shapes

if I have the follow code in the index.html.erb file

<%= form_for :table do |f| %>

<%= f.collection_select(:basket, @basket, :id, :shape, {:prompt => true}) %>

<%= f.collection_select(:apple, @apple, :id, :color, {:prompt => true}) %>

<%= f.submit %>

<% end %>

*** appear the page correctly ***

meanwhile if I have the follow code

<%= form_for @table do |f| %>

<%= f.collection_select(:basket, @basket, :id, :shape, {:prompt => true}) %>

<%= f.collection_select(:apple, @apple, :id, :color, {:prompt => true}) %>

<%= f.submit %>

<% end %>

the page show the follow error page

//////////// undefined method `model_name' for NilClass:Class

That means that @table is nil. This form cannot work if @table has not been setup to be an object of appropriate type. :table is a symbol used here to represent a type of object, @table is a variable that must have been setup in the controller in order to use it in the view.

Colin.

Colin

4

Thanks for all answer I don't use the scaffold for that app

here is my table CONTROLLER

class TableController < ApplicationController

  def index     @basket = Basket.find(:all)     @apple = Apple.find(:all)   end

  def new     @table = Table.new   end end

here my MODEL

class Table < ActiveRecord::Base

belongs_to :apples belongs_to :baskets

end

maybe above you can see a logic error? or syntax error?

thanks anyway,

C

Colin Law wrote in post #1052589:

5

If you are going to use @table in index.html.erb (that is handled by def index ) you have to add to the index method

def index

…

@table = Table.new

end

but I don’t know why does it works with the symbol and not with the instance

Javier Q.

6

Hi Javier,

you are right I just added it anyway when I reloaded the page now I have another error

undefined method `basket' for #<Table id: nil, created_at: nil, updated_at: nil>

I edit the basket and apple controller with

def index

@basket = Basket.find(:all)

end

def index

@apple = Apple.find(:all)

end

but I have always the same error

thanks

C

Javier Quarite wrote in post #1052696:

7

I’m not sure what are the fields of your Table … table :D, but according with your error it only has and id, and the timestamps(created_at, update_at)

If you want to save inside Table the basket_id and the color_id then you have to add columns for it, after that instead of the symbols :basket and :apple, write :basket_id and :apple_id (I’m not sure if thats correc because I don’t usually use the form helpers from rails, I use a gem simple_form).

You should take a look rails guides on views and forms

Javier Q.

8

Hi,

I figured out this error

undefined method `basket' for #<Table id: nil, created_at: nil, updated_at: nil>

simply add two columns (apple & basket) in the table called Table :slight_smile:

now appear correctly the webpage with the drop down menu so

If you have in the app/views/table/new.html.erb

1. <%= form_for @table do |f| %> 2. <%= f.collection_select(:basket, @basket, :id, :shape, {:prompt => true}) %> 3. <%= f.collection_select(:apple, @apple, :id, :color, {:prompt => true}) %>

it works but

A. in the model Table you have the follow code

def new

@apple = Apple.find(:all) @Basket = Basket.find(:all) @table = Table.new

end

B. in the table called 'Table' obviously you have 2 record 'apple' and ''

NOW

even if I don't have the right code as letter A. and letter B. if I write in the line 1.

<%= form_for :table do |f| %>

and not

<%= form_for @table do |f| %>

the page appear correctly and load also the data from apple & basket table in the drop down menu

I don't know why but is only a doubt to understand the difference between a symbol and an instance

thanks a lot anyway

C