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/***************************************************************************************************
Copyright (C) 2025 The Qt Company Ltd.
SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
***************************************************************************************************/
using System.Collections.Concurrent;
using System.ComponentModel;
using System.Linq.Expressions;
using System.Reflection;
namespace Qt.DotNet.Utils
{
public class LazyFactory : INotifyPropertyChanged
{
private ConcurrentDictionary<(object, PropertyInfo), object> Objs { get; } = new();
public event PropertyChangedEventHandler PropertyChanged;
private readonly object criticalSection = new();
public T Get<T>(Expression<Func<T>> propertyRef, Func<T> initFunc = null)
{
if (propertyRef?.Body is not MemberExpression lazyPropertyExpr)
throw new ArgumentException("Expected member lambda", nameof(propertyRef));
if (lazyPropertyExpr?.Member is not PropertyInfo lazyProperty)
throw new ArgumentException("Invalid property reference", nameof(propertyRef));
object owner = lazyProperty.DeclaringType;
if (lazyPropertyExpr.Expression is ConstantExpression { Value: not null } lazyThis)
owner = lazyThis.Value;
lock (criticalSection) {
if (initFunc != null)
return (T)Objs.GetOrAdd((owner, lazyProperty), k => initFunc());
else
return (T)Objs.GetOrAdd((owner, lazyProperty), k => default(T));
}
}
public void Set<T>(Expression<Func<T>> propertyRef, T value)
{
if (propertyRef?.Body is not MemberExpression lazyPropertyExpr)
throw new ArgumentException("Expected member lambda", nameof(propertyRef));
if (lazyPropertyExpr?.Member is not PropertyInfo lazyProperty)
throw new ArgumentException("Invalid property reference", nameof(propertyRef));
object owner = lazyProperty.DeclaringType;
if (lazyPropertyExpr.Expression is ConstantExpression { Value: not null } lazyThis)
owner = lazyThis.Value;
if (Objs.TryGetValue((owner, lazyProperty), out var current) && current.Equals(value))
return;
Objs[(owner, lazyProperty)] = value;
PropertyChanged?.Invoke(owner, new PropertyChangedEventArgs(lazyProperty.Name));
}
}
}
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