A table helper file for HAML templates that allows you to make tables of a data collection painfully easy.

some_view.html.haml

%h1 All Users
- table_for User.all do
  - column "Username" => :username
  - column "Email"    => ->(m) { mail_to m.email }
  - column "Notes"    => :notes

table_helper.rb

module TableHelper
  # Creates a table based on a model by building the required columns.
  # Could be extended further to support Pagination, that's a homework assignment.
  #
  # Accepts a block which includes the #column method. To this method, you pass the
  # string for the column heading, and a symbol or lambda (with one parameter) for
  # the table data.
  #
  # Currently a HAML helper.
  #
  # @example
  #   - table_for User.new do
  #     - column "Username" => :username
  #     - column "Email"    => ->(m) { mail_to m.email }
  #     - column "Notes"    => :notes
  #
  def table_for(model, &columns)
    column_hash = TableColumns.new(&columns).to_h

    haml_tag :table do
      haml_tag :thead do
        haml_tag :tr do
          column_hash.keys.each do |th|
            haml_tag :th, th
          end
        end
      end

      haml_tag :tbody do
        model.each do |m|
          haml_tag :tr do
            column_hash.values.each do |td|
              val = if td.kind_of?(Symbol)
                m.send(td)
              else
                td.call(m)
              end

              haml_tag :td, val
            end
          end
        end
      end
    end
  end

  # Helper class for the TableHelper to parse the block provided
  # into a column hash.
  #
  # Extend this to provide other data processing options, other than
  # the default #column method.
  #
  class TableColumns
    include Rails.application.routes.url_helpers
    include ActionView::Helpers::TextHelper
    include ActionView::Helpers::TagHelper
    include ActionView::Helpers::UrlHelper

    def initialize(&block)
      @cols = Hash.new
      self.instance_eval(&block)
    end

    def column(*args)
      if args.first.kind_of? Hash
        @cols[args.first.keys.first] = args.first.values.first
      else
        @cols[args[0]] = args[1]
      end
    end

    def to_h
      @cols
    end
  end

end