application_helper.rb

module ApplicationHelper
  # activated の条件が真のとき、.active クラス付きの <a> タグを生成
  #
  # 例:
  # = activated_link_to params[:sort] == 'newly', hogehoge_path(sort: :newly) do
  #   %span 新着順
  #
  def activated_link_to(activated, name = nil, options = {}, html_options = {}, &block)
    if block_given?
      html_options = options
      options      = name
    end
    options ||= {}

    if activated
      case html_options[:class]
      when String
        html_options[:class] << " active"
      when Array
        html_options[:class] << "active"
      when nil
        html_options[:class] = "active"
      end
    end

    if block_given?
      link_to(options, html_options, &block)
    else
      link_to(name, options, html_options)
    end
  end
end