simple_form.rb

inputs = %w[
  CollectionSelectInput
  DateTimeInput
  FileInput
  GroupedCollectionSelectInput
  NumericInput
  PasswordInput
  RangeInput
  StringInput
  TextInput
]
 
inputs.each do |input_type|
  superclass = "SimpleForm::Inputs::#{input_type}".constantize
 
  new_class = Class.new(superclass) do
    def input_html_classes
      super.push('form-control')
    end
  end
 
  Object.const_set(input_type, new_class)
end

SimpleForm.setup do |config|
  config.wrappers :default, tag: :div, class: 'form-group', error_class: 'has-error' do |b|
    b.use :html5
    b.use :placeholder

    b.use :label

    b.wrapper tag: :div, class: 'col-md-7' do |bb|
      bb.use :input
      bb.use :hint,  wrap_with: { tag: :span, class: 'help-block' }
    end

    b.use :error, wrap_with: { tag: :span, class: 'help-block has-error' }
  end

  config.wrappers :checkbox, tag: :div, class: 'form-group', error_class: 'has-error' do |b|
    b.wrapper tag: :div, class: 'col-md-offset-3 col-md-7' do |ba|
      ba.wrapper :div, class: 'checkbox' do |bb|
        bb.wrapper tag: :label do |bc|
          bc.use :input, class: ''
          bc.use :label_text
        end
      end

      ba.use :hint, wrap_with: { tag: :span, class: 'help-block' }
      ba.use :error, wrap_with: { tag: :span, class: 'help-block has-error' }
    end
  end

  config.form_class    = 'form-horizontal'
  config.label_class   = 'col-md-3 control-label'
  config.button_class  = 'btn btn-primary'

  config.default_wrapper = :default
end