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 counter to the latest 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
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.
This particular implementation checks for added and updated files, but not
removed files. Directories lookup are compiled to a glob for performance.
Therefore, while someone can add new files to the files
array
after initialization (and parts of Rails do depend on this feature), adding
new directories after initialization is not allowed.
Notice that other objects that implements FileUpdateChecker API may not even allow
new files to be added after initialization. If this is the case, we
recommend freezing the files
after initialization to avoid
changes that won't make effect.
# File lib/active_support/file_update_checker.rb, line 55 def initialize(files, dirs={}, &block) @files = files @glob = compile_glob(dirs) @block = block @updated_at = nil @last_update_at = updated_at end
Executes the given block and updates the counter to latest timestamp.
# File lib/active_support/file_update_checker.rb, line 76 def execute @last_update_at = updated_at @block.call ensure @updated_at = nil end
Execute the block given if updated.
# File lib/active_support/file_update_checker.rb, line 84 def execute_if_updated if updated? execute true else false end end
Check if any of the entries were updated. If so, the updated_at value is
cached until the block is executed via execute
or
execute_if_updated
# File lib/active_support/file_update_checker.rb, line 65 def updated? current_updated_at = updated_at if @last_update_at < current_updated_at @updated_at = updated_at true else false end end