perf: use less rx operators (#104)

reactivemarbles · Dec 14, 2020 · 2e4a25e · 2e4a25e
1 parent 599391a
commit 2e4a25e
Showing 1 changed file with 69 additions and 8 deletions.
diff --git a/src/ReactiveMarbles.PropertyChanged/NotifyPropertyChangedExtensions.cs b/src/ReactiveMarbles.PropertyChanged/NotifyPropertyChangedExtensions.cs
@@ -35,7 +35,39 @@ public static IObservable<TReturn> WhenPropertyValueChanges<TObj, TReturn>(
  throw new ArgumentNullException(nameof(propertyExpression));
  }
 
- return WhenPropertyChanges(objectToMonitor, propertyExpression).Select(x => x.Value);
+ IObservable<INotifyPropertyChanged> currentObservable = Observable.Return((INotifyPropertyChanged)objectToMonitor);
+
+ var expressionChain = propertyExpression.Body.GetExpressionChain();
+
+ if (expressionChain.Count == 0)
+ {
+ throw new ArgumentException("There are no properties in the expressions", nameof(propertyExpression));
+ }
+
+ var i = 0;
+ foreach (var memberExpression in expressionChain)
+ {
+ var memberInfo = memberExpression.Member;
+
+ if (i == expressionChain.Count - 1)
+ {
+ return Observable.Return(memberInfo)
+ .CombineLatest(currentObservable, (memberInfo, parent) => (memberInfo, value: parent))
+ .Where(x => x.value != null)
+ .Select(x => GenerateObservable(x.value, x.memberInfo, GetMemberFuncCache<INotifyPropertyChanged, TReturn>.GetCache(x.memberInfo)))
+ .Switch();
+ }
+
+ currentObservable = Observable.Return(memberInfo)
+ .CombineLatest(currentObservable, (memberInfo, parent) => (memberInfo, value: parent))
+ .Where(x => x.value != null)
+ .Select(x => GenerateObservable(x.value, x.memberInfo, GetMemberFuncCache<INotifyPropertyChanged, INotifyPropertyChanged>.GetCache(x.memberInfo)))
+ .Switch();
+
+ i++;
+ }
+
+ throw new ArgumentException("Invalid expression", nameof(propertyExpression));
  }
 
  /// <summary>
@@ -77,14 +109,14 @@ public static IObservable<TReturn> WhenPropertyValueChanges<TObj, TReturn>(
  return Observable.Return(memberInfo)
  .CombineLatest(currentObservable, (memberInfo, parent) => (memberInfo, sender: parent.Sender, value: parent.Value))
  .Where(x => x.value != null)
- .Select(x => GenerateObservable(x.value, x.memberInfo, GetMemberFuncCache<INotifyPropertyChanged, TReturn>.GetCache(x.memberInfo)))
+ .Select(x => GenerateObservableWithSender(x.value, x.memberInfo, GetMemberFuncCache<INotifyPropertyChanged, TReturn>.GetCache(x.memberInfo)))
  .Switch();
  }
 
  currentObservable = Observable.Return(memberInfo)
  .CombineLatest(currentObservable, (memberInfo, parent) => (memberInfo, sender: parent.Sender, value: parent.Value))
  .Where(x => x.value != null)
- .Select(x => GenerateObservable(x.value, x.memberInfo, GetMemberFuncCache<INotifyPropertyChanged, INotifyPropertyChanged>.GetCache(x.memberInfo)))
+ .Select(x => GenerateObservableWithSender(x.value, x.memberInfo, GetMemberFuncCache<INotifyPropertyChanged, INotifyPropertyChanged>.GetCache(x.memberInfo)))
  .Switch();
 
  i++;
@@ -93,22 +125,51 @@ public static IObservable<TReturn> WhenPropertyValueChanges<TObj, TReturn>(
  throw new ArgumentException("Invalid expression", nameof(propertyExpression));
  }
 
- private static IObservable<(object Sender, T Value)> GenerateObservable<T>(
+ private static IObservable<T> GenerateObservable<T>(
  INotifyPropertyChanged parent,
  MemberInfo memberInfo,
  Func<INotifyPropertyChanged, T> getter)
  {
  var memberName = memberInfo.Name;
- return Observable.FromEvent<PropertyChangedEventHandler, (object Sender, PropertyChangedEventArgs Args)>(
+ return Observable.FromEvent<PropertyChangedEventHandler, T>(
  handler =>
  {
- void Handler(object sender, PropertyChangedEventArgs e) => handler((sender, e));
+ void Handler(object sender, PropertyChangedEventArgs e)
+ {
+ if (e.PropertyName == memberName)
+ {
+ handler(getter(parent));
+ }
+ }
+
+ return Handler;
+ },
+ x => parent.PropertyChanged += x,
+ x => parent.PropertyChanged -= x)
+ .StartWith(getter(parent));
+ }
+
+ private static IObservable<(object Sender, T Value)> GenerateObservableWithSender<T>(
+ INotifyPropertyChanged parent,
+ MemberInfo memberInfo,
+ Func<INotifyPropertyChanged, T> getter)
+ {
+ var memberName = memberInfo.Name;
+ return Observable.FromEvent<PropertyChangedEventHandler, (object Sender, T Value)>(
+ handler =>
+ {
+ void Handler(object sender, PropertyChangedEventArgs e)
+ {
+ if (e.PropertyName == memberName)
+ {
+ handler((sender, getter(parent)));
+ }
+ }
+
  return Handler;
  },
  x => parent.PropertyChanged += x,
  x => parent.PropertyChanged -= x)
- .Where(x => x.Args.PropertyName == memberName)
- .Select(x => (x.Sender, getter(parent)))
  .StartWith((parent, getter(parent)));
  }
  }