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Using simple_form in a Rails 3 engine

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I’ve been developing an eco-system of engines recently and want to share some components across engines. One of those was simple_form. Unsurprisingly, it’s quite simple to do!

In a file in your lib folder, let’s say my-engine/simple-form.rb, require simple_form and add the config generated underneath. Then, make sure this file is required when your engine is loaded and hey presto, simple forms in your views! I’ve used the default Twitter Bootstrap config here:

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# lib/my-engine/simple-form.rb
require 'simple_form'
# Use this setup block to configure all options available in SimpleForm.
SimpleForm.setup do |config|
  # Wrappers are used by the form builder to generate a
  # complete input. You can remove any component from the
  # wrapper, change the order or even add your own to the
  # stack. The options given below are used to wrap the
  # whole input.
  config.wrappers :default, :class => :input,
    :hint_class => :field_with_hint, :error_class => :field_with_errors do |b|
    ## Extensions enabled by default
    # Any of these extensions can be disabled for a
    # given input by passing: `f.input EXTENSION_NAME => false`.
    # You can make any of these extensions optional by
    # renaming `b.use` to `b.optional`.

    # Determines whether to use HTML5 (:email, :url, ...)
    # and required attributes
    b.use :html5

    # Calculates placeholders automatically from I18n
    # You can also pass a string as f.input :placeholder => "Placeholder"
    b.use :placeholder

    ## Optional extensions
    # They are disabled unless you pass `f.input EXTENSION_NAME => :lookup`
    # to the input. If so, they will retrieve the values from the model
    # if any exists. If you want to enable the lookup for any of those
    # extensions by default, you can change `b.optional` to `b.use`.

    # Calculates maxlength from length validations for string inputs
    b.optional :maxlength

    # Calculates pattern from format validations for string inputs
    b.optional :pattern

    # Calculates min and max from length validations for numeric inputs
    b.optional :min_max

    # Calculates readonly automatically from readonly attributes
    b.optional :readonly

    ## Inputs
    b.use :label_input
    b.use :hint,  :wrap_with => { :tag => :span, :class => :hint }
    b.use :error, :wrap_with => { :tag => :span, :class => :error }
  end

  config.wrappers :bootstrap, :tag => 'div', :class => 'control-group', :error_class => 'error' do |b|
    b.use :html5
    b.use :placeholder
    b.use :label
    b.wrapper :tag => 'div', :class => 'controls' do |ba|
      ba.use :input
      ba.use :error, :wrap_with => { :tag => 'span', :class => 'help-inline' }
      ba.use :hint,  :wrap_with => { :tag => 'p', :class => 'help-block' }
    end
  end

  config.wrappers :prepend, :tag => 'div', :class => "control-group", :error_class => 'error' do |b|
    b.use :html5
    b.use :placeholder
    b.use :label
    b.wrapper :tag => 'div', :class => 'controls' do |input|
      input.wrapper :tag => 'div', :class => 'input-prepend' do |prepend|
        prepend.use :input
      end
      input.use :hint,  :wrap_with => { :tag => 'span', :class => 'help-block' }
      input.use :error, :wrap_with => { :tag => 'span', :class => 'help-inline' }
    end
  end

  config.wrappers :append, :tag => 'div', :class => "control-group", :error_class => 'error' do |b|
    b.use :html5
    b.use :placeholder
    b.use :label
    b.wrapper :tag => 'div', :class => 'controls' do |input|
      input.wrapper :tag => 'div', :class => 'input-append' do |append|
        append.use :input
      end
      input.use :hint,  :wrap_with => { :tag => 'span', :class => 'help-block' }
      input.use :error, :wrap_with => { :tag => 'span', :class => 'help-inline' }
    end
  end

  # Wrappers for forms and inputs using the Twitter Bootstrap toolkit.
  # Check the Bootstrap docs (http://twitter.github.com/bootstrap)
  # to learn about the different styles for forms and inputs,
  # buttons and other elements.
  config.default_wrapper = :bootstrap

  # Define the way to render check boxes / radio buttons with labels.
  # Defaults to :nested for bootstrap config.
  #   :inline => input + label
  #   :nested => label > input
  config.boolean_style = :nested

  # Default class for buttons
  config.button_class = 'btn'

  # Method used to tidy up errors.
  # config.error_method = :first

  # Default tag used for error notification helper.
  config.error_notification_tag = :div

  # CSS class to add for error notification helper.
  config.error_notification_class = 'alert alert-error'

  # ID to add for error notification helper.
  # config.error_notification_id = nil

  # Series of attempts to detect a default label method for collection.
  # config.collection_label_methods = [ :to_label, :name, :title, :to_s ]

  # Series of attempts to detect a default value method for collection.
  # config.collection_value_methods = [ :id, :to_s ]

  # You can wrap a collection of radio/check boxes in a pre-defined tag, defaulting to none.
  # config.collection_wrapper_tag = nil

  # You can define the class to use on all collection wrappers. Defaulting to none.
  # config.collection_wrapper_class = nil

  # You can wrap each item in a collection of radio/check boxes with a tag,
  # defaulting to :span. Please note that when using :boolean_style = :nested,
  # SimpleForm will force this option to be a label.
  # config.item_wrapper_tag = :span

  # You can define a class to use in all item wrappers. Defaulting to none.
  # config.item_wrapper_class = nil

  # How the label text should be generated altogether with the required text.
  # config.label_text = lambda { |label, required| "#{required} #{label}" }

  # You can define the class to use on all labels. Default is nil.
  config.label_class = 'control-label'

  # You can define the class to use on all forms. Default is simple_form.
  # config.form_class = :simple_form

  # You can define which elements should obtain additional classes
  # config.generate_additional_classes_for = [:wrapper, :label, :input]

  # Whether attributes are required by default (or not). Default is true.
  # config.required_by_default = true

  # Tell browsers whether to use default HTML5 validations (novalidate option).
  # Default is enabled.
  config.browser_validations = false

  # Collection of methods to detect if a file type was given.
  # config.file_methods = [ :mounted_as, :file?, :public_filename ]

  # Custom mappings for input types. This should be a hash containing a regexp
  # to match as key, and the input type that will be used when the field name
  # matches the regexp as value.
  # config.input_mappings = { /count/ => :integer }

  # Default priority for time_zone inputs.
  # config.time_zone_priority = nil

  # Default priority for country inputs.
  # config.country_priority = nil

  # Default size for text inputs.
  # config.default_input_size = 50

  # When false, do not use translations for labels.
  # config.translate_labels = true

  # Automatically discover new inputs in Rails' autoload path.
  # config.inputs_discovery = true

  # Cache SimpleForm inputs discovery
  # config.cache_discovery = !Rails.env.development?
end