How can I force the correct hash access syntax from my text_field form helper?

I am working on a Rails project, using Mongo. I am faced with an issue in my view form helper, in that (whether this access is through Rails or Mongoid, I am not sure) I am attempting to access a value within a Hash field on my model, but I am getting an undefined method error, because it is attempting to access the hash using dot notation, instead of bracket notation.

The model:

class AgencySetting
  include Mongoid::Document
  include Mongoid::Timestamps

  field :uuid,            type: String
  field :mailing_address, type: Hash
  field :service_address, type: Hash
  field :active,          type: Boolean, default: true

  embeds_many :contracts

  validates :uuid, presence: true, uniqueness: true
end

The form (this is probably not the ideal way to handle a Hash attribute field, there is another f.fields_for attached to service_address that I have excluded for brevity):

      = form_with model: @agency_setting, url: agency_setting_url, method: :post do |f|

        = f.fields_for :mailing_address, @agency_setting.mailing_address do |m_fields|
          = m_fields.text_field :line_1, class: 'form-control my-1', placeholder: 'Contract street line one'
          = m_fields.text_field :line_2, class: 'form-control my-1', placeholder: 'Contract street line two'
          = m_fields.text_field :city, class: 'form-control my-1', placeholder: 'Contract city'
          = m_fields.text_field :state, class: 'form-control my-1', placeholder: 'Contract state'
          = m_fields.text_field :zip, class: 'form-control my-1', placeholder: 'Contract zip'

        = f.submit 'Save settings', class: 'btn btn-primary mt-2'

It throws the error on the first line of m_fields, specifically it gives, undefined method 'line_1' for {"line_1"=>"123", "line_2"=>"123", "city"=>"123", "state"=>"123", "zip"=>"123"}:BSON::Document. Clearly, the reason for this is that it is attempting to access mailing_address with mailing_address.line_1 instead of mailing_address[:line_1] which runs fine in the console. Is it possible to force the helper to use the latter syntax instead?

Solution

Is it possible to force the helper to use the latter syntax instead?

No. But you can provide the value manually:

= form_with model: @agency_setting, url: agency_setting_url, method: :post do |f|
  = f.fields_for :mailing_address, @agency_setting.mailing_address do |m_fields|
    = m_fields.text_field :line_1, 
                          class: 'form-control my-1', 
                          placeholder: 'Contract street line one',
                          value: m_fields.object[:line_1]

Or you can convert the Hash into a OpenStruct:

= form_with model: @agency_setting, url: agency_setting_url, method: :post do |f|
  = f.fields_for :mailing_address, OpenStruct.new(@agency_setting.mailing_address) do |m_fields|
    = m_fields.text_field :line_1, 
                          class: 'form-control my-1', 
                          placeholder: 'Contract street line one'
    # ...

But this really just begs the question why you're shooting yourself in the foot instead of just modeling your data better.

class Address
  include Mongoid::Document
  include Mongoid::Attributes::Dynamic
  include Mongoid::Timestamps

  field :line_1,            type: String
  field :line_2,            type: String
  # ...
end

class AgencySetting
  include Mongoid::Document
  include Mongoid::Timestamps

  field :uuid,            type: String
  field :active,          type: Boolean, default: true

  embeds_many :contracts
  embeds_one :mailing_address, class_name: 'Address'
  embeds_one :service_address, class_name: 'Address'
end

Having an actual model will make your life so much easier when it comes to adding validations and dealing with the input.