box.watch()

Subscribe to events broadcast by a local host.

Parameters:

• key (string) — key name of the event to subscribe to

• func (function) — callback to invoke when the key value is updated

Returns

a watcher handle. The handle consists of one method – unregister(), which unregisters the watcher.

To read more about watchers, see the Functions for watchers section.

Example:

 
-- Broadcast value 42 for the 'foo' key.box.broadcast('foo', 42)local log = require('log')-- Subscribe to updates of the 'foo' key.local w = box.watch('foo', function(key, value)    assert(key == 'foo')    log.info("The box.id value is '%d'", value)end)

If you don't need the watcher anymore, you can unregister it using the command below:

 
w:unregister()