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 55: def initialize(files, dirs={}, &block) 56: @files = files 57: @glob = compile_glob(dirs) 58: @block = block 59: @updated_at = nil 60: @last_update_at = updated_at 61: end
Executes the given block and updates the counter to latest timestamp.
# File lib/active_support/file_update_checker.rb, line 76 76: def execute 77: @last_update_at = updated_at 78: @block.call 79: ensure 80: @updated_at = nil 81: end
Execute the block given if updated.
# File lib/active_support/file_update_checker.rb, line 84 84: def execute_if_updated 85: if updated? 86: execute 87: true 88: else 89: false 90: end 91: 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 65: def updated? 66: current_updated_at = updated_at 67: if @last_update_at < current_updated_at 68: @updated_at = updated_at 69: true 70: else 71: false 72: end 73: end
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