class ActiveSupport::FileUpdateChecker - activesupport-4.2.4 Documentation

# class ActiveSupport::FileUpdateChecker

FileUpdateChecker specifies the API used by Rails to watch files and control reloading. The API depends on four methods:

- `initialize` which expects two parameters and one block as described below.

- `updated?` which returns a boolean if there were updates in the filesystem or not.

- `execute` which executes the given block on initialization and updates the latest watched files and timestamp.

- `execute_if_updated` which just executes the block if it was updated.

After initialization, a call to `execute_if_updated` must execute the block only if there was really a change in the filesystem.

This class is used by Rails to reload the I18n framework whenever they are changed upon a new request.

    i18n_reloader = ActiveSupport::FileUpdateChecker.new(paths) do
      I18n.reload!
    end

    ActionDispatch::Reloader.to_prepare do
      i18n_reloader.execute_if_updated
    end

### Public Class Methods

new(files, dirs={}, &block) click to toggle source

It accepts two parameters on initialization. The first is an array of files and the second is an optional hash of directories. The hash must have directories as keys and the value is an array of extensions to be watched under that directory.

This method must also receive a block that will be called once a path changes. The array of files and list of directories cannot be changed after FileUpdateChecker has been initialized.

    # File lib/active_support/file_update_checker.rb, line 38
    def initialize(files, dirs={}, &block)
      @files = files.freeze
      @glob  = compile_glob(dirs)
      @block = block

      @watched    = nil
      @updated_at = nil

      @last_watched   = watched
      @last_update_at = updated_at(@last_watched)
    end

### Public Instance Methods

execute() click to toggle source

Executes the given block and updates the latest watched files and timestamp.

    # File lib/active_support/file_update_checker.rb, line 72
    def execute
      @last_watched   = watched
      @last_update_at = updated_at(@last_watched)
      @block.call
    ensure
      @watched = nil
      @updated_at = nil
    end

execute_if_updated() click to toggle source

Execute the block given if updated.

    # File lib/active_support/file_update_checker.rb, line 82
    def execute_if_updated
      if updated?
        execute
        true
      else
        false
      end
    end

updated?() click to toggle source

Check if any of the entries were updated. If so, the watched and/or #updated_at values are cached until the block is executed via `execute` or `execute_if_updated`.

    # File lib/active_support/file_update_checker.rb, line 53
    def updated?
      current_watched = watched
      if @last_watched.size != current_watched.size
        @watched = current_watched
        true
      else
        current_updated_at = updated_at(current_watched)
        if @last_update_at < current_updated_at
          @watched    = current_watched
          @updated_at = current_updated_at
          true
        else
          false
        end
      end
    end

### Private Instance Methods

compile_ext(array) click to toggle source

    # File lib/active_support/file_update_checker.rb, line 131
    def compile_ext(array)
      array = Array(array)
      return if array.empty?
      ".{#{array.join(",")}}"
    end

compile_glob(hash) click to toggle source

    # File lib/active_support/file_update_checker.rb, line 117
    def compile_glob(hash)
      hash.freeze # Freeze so changes aren't accidentally pushed
      return if hash.empty?

      globs = hash.map do |key, value|
        "#{escape(key)}/**/*#{compile_ext(value)}"
      end
      "{#{globs.join(",")}}"
    end

escape(key) click to toggle source

    # File lib/active_support/file_update_checker.rb, line 127
    def escape(key)
      key.gsub(',','\,')
    end

max_mtime(paths) click to toggle source

This method returns the maximum mtime of the files in `paths`, or `nil` if the array is empty.

Files with a mtime in the future are ignored. Such abnormal situation can happen for example if the user changes the clock by hand. It is healthy to consider this edge case because with mtimes in the future reloading is not triggered.

    # File lib/active_support/file_update_checker.rb, line 112
    def max_mtime(paths)
      time_now = Time.now
      paths.map {|path| File.mtime(path)}.reject {|mtime| time_now < mtime}.max
    end

updated_at(paths) click to toggle source

    # File lib/active_support/file_update_checker.rb, line 101
    def updated_at(paths)
      @updated_at || max_mtime(paths) || Time.at(0)
    end

watched() click to toggle source

    # File lib/active_support/file_update_checker.rb, line 93
    def watched
      @watched || begin
        all = @files.select { |f| File.exist?(f) }
        all.concat(Dir[@glob]) if @glob
        all
      end
    end