FSSM based FileWatcher for Rails

1_README.md

Rails 3.2 ships with a simple FileWatcher that only reloads your app if any of the files changed.

Besides, it also provides a mechanism to hook up your own file watcher mechanism, so we can use tools like FSSM that hooks into Mac OS X fsevents and does the hard work for us. This is an example on how to hook your own mechanism:

1. Copy the 2_file_watcher.rb file below to lib/file_watcher.rb

2. Add the following inside your Application in config/application.rb

   require "file_watcher" config.file_watcher = FileWatcher

3. Add "fssm" to your Gemfile

4. Profit!

2_file_watcher.rb

require "active_support/core_ext/array/wrap"
require "active_support/core_ext/array/extract_options"
require "fssm"

class FileWatcher
  def initialize(paths, _calculate, &block)
    @block = block
    @last_update_at = Time.at(0)
    @updated_at = Time.at(1)
    start_monitor(paths) { |base, relative| update(base, relative) }
  end

  def updated?
    raise "Error on FileWatcher. FSSM thread is dead." unless @thread.alive?
    @updated_at > @last_update_at
  end

  def execute_if_updated
    if updated?
      execute
      true
    else
      false
    end
  end

  def execute
    @last_update_at = @updated_at
    @block.call
  end

  private

  def update(base, relative)
    timestamp = File.mtime(File.join(base, relative))
    @updated_at = timestamp if timestamp > @updated_at
  end

  def compile_glob(exts)
    array = Array.wrap(array)
    return "**/*" if array.empty?
    "**/*.{#{array.join(",")}}"
  end

  def start_monitor(paths, &block)
    exprs = Hash.new { |h,k| h[k] = [] }
    dirs  = paths.extract_options!

    paths.each do |path|
      exprs[File.dirname(path)] << File.basename(path)
    end

    dirs.each do |path, exts|
      exprs[path] << compile_glob(exts)
    end

    paths.freeze
    dirs.freeze

    @monitor = FSSM::Monitor.new

    exprs.each do |dir, globs|
      @monitor.path dir do
        glob "{#{globs.join(",")}}"
        update(&block)
        create(&block)
      end
    end

    @thread = Thread.new { @monitor.run }
  end
end