method open


dynamic open(callback)

Initiates observation and returns the initial value. The callback will be passed the updated value, and may optionally be declared to take a second argument, which will contain the previous value.

Implementation note: a third argument can also be declared, which will receive a list of objects and paths, such that list[2 * i] will access the object and list[2 * i + 1] will access the path, where i is the order of the addPath call. This parameter is only used by package:polymer as a performance optimization, and should not be relied on in new code.

Source

open(callback) => super.open(callback);