Ruby 1.8.7 リファレンスマニュアル > ライブラリ一覧 > test/unit/util/observableライブラリ > Test::Unit::Util::Observableモジュール > add_listener

instance method Test::Unit::Util::Observable#add_listener

add_listener(channel_name, listener_key=NOTHING, &listener)

Adds the passed proc as a listener on the channel indicated by channel_name. listener_key is used to remove the listener later; if none is specified, the proc itself is used.

Whatever is used as the listener_key is returned, making it very easy to use the proc itself as the listener_key:

listener = add_listener("Channel") { ... }
remove_listener("Channel", listener)