/
root_observable_state.dart
165 lines (136 loc) · 3.86 KB
/
root_observable_state.dart
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part of core;
typedef ValueChanged<T> = void Function(T previous, T current);
typedef ValueSetter<T> = T Function(T value);
/// Core class in `beholder`.
/// Every change is initiated by [RootObservableState]
/// Usually, you don't need to use it directly
@internal
sealed class BaseObservableState<T> with DebugReprMixin implements ObservableState<T> {
BaseObservableState(this._value, {Equals<T>? equals})
: _equals = equals ?? Observable.defaultEquals;
@override
T get value => _value;
@override
bool setValue(T value) {
assert(!_isDisposed, "Cannot set value once state is disposed");
final oldValue = _value;
final willUpdate = !_equals(oldValue, value);
if (willUpdate) {
_value = value;
onValueSet(oldValue, value);
for (final plugin in _plugins) {
plugin.onValueChanged(oldValue, value);
}
} else {
for (final plugin in _plugins) {
plugin.onValueRejected(value);
}
}
return willUpdate;
}
@override
set value(T value) {
setValue(value);
}
void onValueSet(T from, T to);
@override
Disposer listen(ValueChanged<T> onChanged) {
assert(!_isDisposed, "$this is already disposed");
final observer = ValueChangedObserver(onChanged);
addObserver(observer);
return () => removeObserver(observer);
}
@override
Disposer listenSync(ValueChanged<T> onChanged) {
assert(!_isDisposed, "$this is already disposed");
final isNew = _eagerListeners.add(onChanged);
assert(isNew, "Listener already added");
return () => _eagerListeners.remove(onChanged);
}
final Equals<T> _equals;
T _value;
@override
void dispose() {
assert(() {
_isDisposed = true;
debugLog("$this disposed");
return true;
}());
_eagerListeners.clear();
_controller.dispose();
_observers.clear();
for (final plugin in _plugins) {
plugin.onDisposed();
}
_plugins.clear();
}
@override
Stream<T> asStream() => _controller.get().stream;
@override
void addObserver(ObserverMixin observer) {
assert(!_isDisposed, "$this is already disposed");
assert(() {
if (!_observers.contains(observer)) {
debugLog("$observer starts observing $this");
}
return true;
}());
observer.onAddedToState(this);
_observers.add(observer);
for (final plugin in _plugins) {
plugin.onObserverAdded(observer);
}
}
@override
void removeObserver(ObserverMixin observer) {
assert(() {
if (_observers.contains(observer)) {
debugLog("$observer stops observing $this");
}
return true;
}());
observer.onRemovedFromState(this);
_observers.remove(observer);
for (final plugin in _plugins) {
plugin.onObserverRemoved(observer);
}
}
@override
late final observers = UnmodifiableSetView(_observers);
final _observers = <ObserverMixin>{};
late final Lazy<StreamController<T>> _controller = Lazy(
() {
Disposer? disposeListen;
late StreamController<T> controller;
controller = StreamController<T>.broadcast(
sync: true,
onCancel: () => disposeListen?.call(),
onListen: () => disposeListen = listen((_, value) => controller.add(value)),
);
return controller;
},
dispose: (controller) => controller.close(),
);
bool _isDisposed = false;
bool get isDisposed => _isDisposed;
final _plugins = <StatePlugin<T>>[];
final _eagerListeners = <ValueChanged<T>>{};
@override
void addPlugin(StatePlugin<T> plugin) {
_plugins.add(plugin);
plugin.attach(this);
}
}
final class RootObservableState<T> extends BaseObservableState<T> {
RootObservableState(
super.value, {
super.equals,
});
@override
void onValueSet(T from, T to) {
ObservableContext().invalidateState(this);
for (final listener in _eagerListeners) {
listener(from, to);
}
}
}