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Class: ActiveSupport::FileUpdateChecker

Relationships & Source Files
Inherits: Object
Defined in: activesupport/lib/active_support/file_update_checker.rb

Overview

File Update Checker

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

ActiveSupport::Reloader.to_prepare do
  i18n_reloader.execute_if_updated
end

Class Method Summary

Instance Attribute Summary

Instance Method Summary

Constructor Details

.new(files, dirs = {}, &block) ⇒ FileUpdateChecker

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.

[ GitHub ] 

  


# File 'activesupport/lib/active_support/file_update_checker.rb', line 44



def initialize(files, dirs = {}, &block)
  unless block
    raise ArgumentError, "A block is required to initialize a FileUpdateChecker"
  end

  @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


  







Instance Attribute Details



  

    #updated?  ⇒ Boolean  (readonly)
  



  

    

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.


  





  


  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/file_update_checker.rb', line 63



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


  







Instance Method Details



  

    #compile_ext(array)   (private)
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/file_update_checker.rb', line 158



def compile_ext(array)
  array = Array(array)
  return if array.empty?
  ".{#{array.join(",")}}"
end


  








  

    #compile_glob(hash)   (private)
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/file_update_checker.rb', line 144



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)   (private)
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/file_update_checker.rb', line 154



def escape(key)
  key.gsub(",", '\,')
end


  








  

    #execute  
  



  

    

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


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/file_update_checker.rb', line 82



def execute
  @last_watched   = watched
  @last_update_at = updated_at(@last_watched)
  @block.call
ensure
  @watched = nil
  @updated_at = nil
end


  








  

    #execute_if_updated  
  



  

    

Execute the block given if updated.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/file_update_checker.rb', line 92



def execute_if_updated
  if updated?
    yield if block_given?
    execute
    true
  else
    false
  end
end


  








  

    #max_mtime(paths)   (private)
  



  

    

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.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/file_update_checker.rb', line 122



def max_mtime(paths)
  time_now = Time.now
  max_mtime = nil

  # Time comparisons are performed with #compare_without_coercion because
  # AS redefines these operators in a way that is much slower and does not
  # bring any benefit in this particular code.
  #
  # Read t1.compare_without_coercion(t2) < 0 as t1 < t2.
  paths.each do |path|
    mtime = File.mtime(path)

    next if time_now.compare_without_coercion(mtime) < 0

    if max_mtime.nil? || max_mtime.compare_without_coercion(mtime) < 0
      max_mtime = mtime
    end
  end

  max_mtime
end


  








  

    #updated_at(paths)   (private)
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/file_update_checker.rb', line 111



def updated_at(paths)
  @updated_at || max_mtime(paths) || Time.at(0)
end


  








  

    #watched   (private)
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/file_update_checker.rb', line 103



def watched
  @watched || begin
    all = @files.select { |f| File.exist?(f) }
    all.concat(Dir[@glob]) if @glob
    all
  end
end