Function trackValueBy

Constructs a tracked value updated by the given value supplier.

If the value is already updated by another supplier, then unbinds from the old one first.

Call the byNone method to unbind the tracked value from the source.

Note that explicitly updating the value would override the value received from the source.

Constructs a tracked value updated by value keepers extracted from events sent by the given supplier.

If the value is already updated by another value supplier, then unbinds from the old one first.

Call the byNone method to unbind the tracked value from the source.

Note that explicitly updating the value would override the value received from the source.