Add display_filter option to simple_form

simple_form_display_filter.rb

module SimpleForm
  class FormBuilder < ActionView::Helpers::FormBuilder
    # tried to monkey patch without copy'n'pasting, broke associations
    def input(attribute_name, options={}, &block)
      options = @defaults.deep_dup.deep_merge(options) if @defaults

      chosen =
        if name = options[:wrapper]
          name.respond_to?(:render) ? name : SimpleForm.wrapper(name)
        else
          wrapper
        end

      # here display_filter logic begins
      display_filter = options.delete(:display_only)

      if (! display_filter) || (display_filter && display_filter.include?(attribute_name))
        chosen.render find_input(attribute_name, options, &block)
      end
    end
  end
end

There we go:

# Helper
module ApplicationHelper
  # A specific form builder to deal with filtering attributes out based on parameters
  class StrongParametersFormBuilder < SimpleForm::FormBuilder
    def input(attribute_name, *args, &block)
      display_filter = self.options[:display_only]

      super unless display_filter && display_filter.include?(attribute_name)
    end
  end

  # Form Helper to be used
  def strong_parameters_form_for(object, options = {}, &block)
    simple_form_for(object, options.merge(:builder => StrongParametersFormBuilder), &block)
  end
end

# view
<%= strong_parameters_form_for(@topic, display_only: [:name] ) do |f| %>
  <%= f.error_notification %>

  <div class="form-inputs">
    <%= f.input :name %>
    <%= f.input :sticky %>
  </div>

  <div class="form-actions">
    <%= f.button :submit %>
  </div>
<% end %>

The issues:

• We had an options argument in def input, so we need to access self.options to access the builder options instead (I've also changed to *args inside the input definition, since options are not being used there.
• The argument should be given as display_only: [:name], not inside the :defaults key. If you want to move it inside defaults, you have to access it the same way when calling the form.

I tested the app and it worked fine for me, let me know how it goes.

# display display_only attributes
if display_filter
  super if display_filter.include?(attribute_name)
else
  super
end

Working example here: https://github.com/denispeplin/display_filter_demo