class ObserverTransform

ObserverTransform is used to dynamically transform observed value(s).

var obj = new ObservableBox(10); var observer = new PathObserver(obj, 'value'); var transform = new ObserverTransform(observer,

   (x) => x * 2, setValue: (x) => x ~/ 2);

// Open returns the current value of 20. transform.open((newValue) => print('new: $newValue'));

obj.value = 20; // prints 'new: 40' async new Future(() {

 transform.value = 4; // obj.value will be 2

});

ObserverTransform can also be used to reduce a set of observed values to a single value:

var obj = new ObservableMap.from({'a': 1, 'b': 2, 'c': 3}); var observer = new CompoundObserver()

 ..addPath(obj, 'a')
 ..addPath(obj, 'b')
 ..addPath(obj, 'c');

var transform = new ObserverTransform(observer,

   (values) => values.fold(0, (x, y) => x + y));

// Open returns the current value of 6. transform.open((newValue) => print('new: $newValue'));

obj'a' = 2; obj'c' = 10; // will print 'new 14' asynchronously