#403 Dynamic Forms pro

Nice cast. I actually had a need for this kind of relation but did it using an EAV style set up rather than serialised arrays.

How would you select or sort by these dynamic values with activerecord?

You can also check out my nested form fields gem: https://github.com/ncri/nested_form_fields

I like the OpenStruct.new usage in this episode. This episode is really a very sharp. Thank you Ryan.

Great cast, interesting and well timed. Quick note that the products/show code is missing form the show notes. But I think we can handle that ourselves ;-)

Wow! I feel like I need to watch this several times in slow motion to absorb it. It's amazing how much you can pack into 14 minutes. It also seems like really understanding dynamic forms could simplify my database architecture.

nice, the smell of the dark side :)
but it's better to avoid this kind of structures because it kills searching, sorting, filtering and other common features... don't you think?

I'm not sure if I'm thinking this through correctly. Would people agree that ProductField names should not be update-able. In the serialized hash the key would remain what it was originally as, so unless the developer goes back and sanitizes all of the product properties in the database, or adds some method_missing translations to the ProductType class a back end client name update would break all of the existing products of that type. Maybe?

This could work nicely with Mongoid to create custom fields in MongoDB.

Now Ryan, if you can just change this from products to personnel records and add workflows, the app I need to write will be done.

Thanks again, Ryan.

Fantastic episode, has helped me a lot. Can I suggest a tweak to the remove_fields coffee script :

$(document).on 'click', 'form .remove_fields', (event) ->
$('input[name$="[_destroy]"]', $(this).siblings()).val('1')
$(this).closest('fieldset').hide()
event.preventDefault()

This makes it less dependent on the position of the hidden destroy field.

Absolutely unbelievable. My partner and I just finished building this very type of functionality into an app. It took us months to figure out a plausible approach, and here it is in 15 minutes. Someone give this man a medal.

A little OT, but here's a link to SO with a way to hack Struct into a Rails project. I've just spent the morning reading up on Struct, OpenStruct, etc. and am amazed with the possibilities!

Didn't really know how to approach using OpenStruct or Struct before this episode. Thanks, Ryan!

http://stackoverflow.com/questions/2240535/how-do-i-use-hash-keys-as-methods-on-a-class/4064219#4064219

It seems that I should prebuild :fields in controller:
def new
@product_type = ProductType.new
@product_type.fields.build
...
end
or it won't show.

If you need to add nested-forms dynamically. You can have a look at
http://stackoverflow.com/questions/15072932/dynamically-adding-fixed-number-of-prepopulated-nested-forms-using-cocoon-and-ra/15275314#15275314

If I would opt by using an external table (properties -> name, value); how it would looks like?

I think the models could be something like this.

  has_many :proprieties 
#...
end

class Property
  belongs_to :product
end

But, what are the best way to bind this to the view?

I immediately cringed when I saw you eschewing the built-in ActiveModel::Validations validators for a custom validate_properties method. Then when your solution to allowing a more complex field to be added was to hard code it I lost all faith.

I actually had to do something similar about a year ago for a project collecting electronic signatures for forms. To meet my needs I used a dynamically defined proxy object that would allow the use of any built in validators on any of the attributes, then passed that to the form builder. I'd love to see this thought through better, but it already more effectively re-uses components that have already been built and tested.

I'm throwing an error trying to recreate this example. Instead of products, I am using forms. Any help or explanation would be very helpful, because this is over my head, but i'd like to learn what is going on here.

NoMethodError in Forms#new

Showing /Users/Admin/Documents/development/form_builder/app/views/forms/fields/_text_field.html.erb where line #3 raised:

undefined method `human_attribute_name' for OpenStruct:Class
Extracted source (around line #3):

1:
2: <%= f.label field.name %>
3: <%= f.text_field field.name %>
4:
Trace of template inclusion: app/views/forms/_form.html.erb, app/views/forms/new.html.erb

Parameters:

{"utf8"=>"✓",
"form_type_id"=>"3"}

If I'm using hstore and implementing the shirt_sizes example, how would I go about "handling the serialization manually" as suggested?

Hi Ryan, thx for this great episode !

One question:
How could i make paperclip to work with your tutorial ?

Thx !

did anyone figure out how to get it to work with ruby 2.0?

I liked this.

I was trying this in Ruby 2, with Rails 4.

The attr_attributes no longer works. Permitting the :fields_attributes didn't cut it, since there is an unknown number of fields. See this

I ended up permitting all parameters with:
params.require(:product_type).permit!

I know it's not safe to do so. If somebody knows a proper way to validate the product type params I would love to hear it.

How would you do model validation to ensure that user must add at least one field?

As I followed the tutorial, it return 'Can't mass-assign protected attributes: destroy' when I attempted to create the product type. How come ?

Hi,

I want to create a dynamic form but there is no model associated with the nested form. I get errors when trying to implement what Ryan has told. Anyone knows how to get around it?

Careful on saving DynamicFormEntries field name.
I had to use the field id because of certain field names were rails reserved words which cannot be used.

I am facing undefined method `fields' for #ProductType:0x007ffb8305a100 at http://localhost:3000/products/new?utf8=%E2%9C%93&product_type_id=1

my app/views/products/_form.html.erb file extraction of the lines which are causing the problem

<%= f.fields_for :properties, OpenStruct.new(@product.properties) do |builder| %>
<% @product.product_type.fields.each do |field| %>
<%= render "products/fields/#{field.field_type}", field: field, f: builder %>

100.times
puts "*********Thank You************************"
end

Awesome Job

Hats off Ryan.

Exactly what I was looking for. Sure hope you come back to do more RailsCasts soon Ryan!

No idea why but I needed to change:

$(this).closest('fieldset').hide()
into:
$(this).parent().hide()

for the removing to work.

it was way too fast for me :'(

hi guys :)
how create a search form for dynamic form ??

Thanks. Now I understand everything is how it all works.

Thanks for the post, this is helpful for my blog