perf: get rid of a couple closures (#103)

* perf: get rid of a couple closures

* replace variable abbreviation with proper name

Co-authored-by: Glenn <[email protected]>

src/ReactiveMarbles.PropertyChanged/GetMemberFuncCache.cs

@@ -12,25 +12,23 @@ namespace ReactiveMarbles.PropertyChanged
  internal static class GetMemberFuncCache<TFrom, TReturn>
  {
 #if !UIKIT
- private static readonly
- ConcurrentDictionary<(Type FromType, string MemberName), Func<TFrom, TReturn>> Cache
- = new ConcurrentDictionary<(Type, string), Func<TFrom, TReturn>>();
+ private static readonly ConcurrentDictionary<MemberInfo, Func<TFrom, TReturn>> Cache = new(new MemberFuncCacheKeyComparer());
 #endif
 
  public static Func<TFrom, TReturn> GetCache(MemberInfo memberInfo)
  {
 #if UIKIT
-  switch (memberInfo)
-  {
-  case PropertyInfo propertyInfo:
-  return input => (TReturn)propertyInfo.GetValue(input);
-  case FieldInfo fieldInfo:
-  return input => (TReturn)fieldInfo.GetValue(input);
-  default:
-  throw new ArgumentException($"Cannot handle member {memberInfo.Name}", nameof(memberInfo));
-  }
+ switch (memberInfo)
+ {
+ case PropertyInfo propertyInfo:
+ return input => (TReturn)propertyInfo.GetValue(input);
+ case FieldInfo fieldInfo:
+ return input => (TReturn)fieldInfo.GetValue(input);
+ default:
+ throw new ArgumentException($"Cannot handle member {memberInfo.Name}", nameof(memberInfo));
+ }
 #else
- return Cache.GetOrAdd((memberInfo.DeclaringType, memberInfo.Name), _ =>
+ return Cache.GetOrAdd(memberInfo, static memberInfo =>
  {
  var instance = Expression.Parameter(typeof(TFrom), "instance");
 

src/ReactiveMarbles.PropertyChanged/MemberFuncCacheKeyComparer.cs

@@ -0,0 +1,22 @@
+// Copyright (c) 2019-2020 ReactiveUI Association Incorporated. All rights reserved.
+// ReactiveUI Association Incorporated licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.Reflection;
+
+namespace ReactiveMarbles.PropertyChanged
+{
+ internal sealed class MemberFuncCacheKeyComparer : IEqualityComparer<MemberInfo>
+ {
+ public bool Equals(MemberInfo x, MemberInfo y)
+ {
+ return (x.DeclaringType, x.Name) == (y.DeclaringType, y.Name);
+ }
+
+ public int GetHashCode(MemberInfo obj)
+ {
+ return (obj.DeclaringType, obj.Name).GetHashCode();
+ }
+ }
+}

src/ReactiveMarbles.PropertyChanged/NotifyPropertyChangedExtensions.cs

@@ -74,17 +74,17 @@ public static IObservable<TReturn> WhenPropertyValueChanges<TObj, TReturn>(
 
  if (i == expressionChain.Count - 1)
  {
- var function = GetMemberFuncCache<INotifyPropertyChanged, TReturn>.GetCache(memberInfo);
- return currentObservable
- .Where(parent => parent.Value != null)
- .Select(parent => GenerateObservable(parent.Value, memberInfo, function))
+ 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)))
  .Switch();
  }
 
- var iFunction = GetMemberFuncCache<INotifyPropertyChanged, INotifyPropertyChanged>.GetCache(memberInfo);
- currentObservable = currentObservable
- .Where(parent => parent.Value != null)
- .Select(parent => GenerateObservable(parent.Value, memberInfo, iFunction))
+ 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)))
  .Switch();
 
  i++;