How to edit a Rails serialized field in a form?

Question

I have a data model in my Rails project that has a serialized field:

class Widget < ActiveRecord::Base
  serialize :options
end

The opti

Answer 1

Well, I had the same problem, and tried not to over-engineer it. The problem is, that although you can pass the serialized hash to fields_for, the fields for function will think, it is an option hash (and not your object), and set the form object to nil. This means, that although you can edit the values, they will not appear after editing. It might be a bug or unexpected behavior of rails and maybe fixed in the future.

However, for now, it is quite easy to get it working (though it took me the whole morning to figure out).

You can leave you model as is and in the view you need to give fields for the object as an open struct. That will properly set the record object (so f2.object will return your options) and secondly it lets the text_field builder access the value from your object/params.

Since I included " || {}", it will work with new/create forms, too.

= form_for @widget do |f|
  = f.fields_for :options, OpenStruct.new(f.object.options || {}) do |f2|
    = f2.text_field :axis_y
    = f2.text_field :axis_x
    = f2.text_field :unit

Have a great day

Answer 2

I was facing the same issue, after some research i found a solution using Rails' store_accessor to make keys of a serialized column accessible as attributes.

With this we can access "nested" attributes of a serialized column …

# post.rb
class Post < ApplicationRecord
  serialize :options
  store_accessor :options, :value1, :value2, :value3
end

# set / get values
post = Post.new
post.value1 = "foo"
post.value1
#=> "foo"
post.options['value1']
#=> "foo"

# strong parameters in posts_controller.rb
params.require(:post).permit(:value1, :value2, :value3)

# form.html.erb
<%= form_with model: @post, local: true do |f| %>
  <%= f.label :value1 %>
  <%= f.text_field :value1 %>
  # …
<% end %>