array_input.md

simple_form_array_input.rb

class ArrayInput < SimpleForm::Inputs::StringInput
  def input
    input_html_options[:type] ||= input_type

    existing_values = Array(object.public_send(attribute_name)).map do |element|
      @builder.text_field(nil, input_html_options.merge(value: element, name: "#{object_name}[#{attribute_name}][]"))
    end

    existing_values.push @builder.text_field(nil, input_html_options.merge(value: nil, name: "#{object_name}[#{attribute_name}][]"))
    existing_values.join.html_safe
  end

  def input_type
    :string
  end
end

View

<%= f.input :elements, as: :array, input_html: { class: "form-control" } %>

Model

def remove_blank_elements
  elements.reject!(&:blank?)
end

def strong_params
  params.require(:model).permit(elements: [])
end