wehub-resource-sync
61 lines
1.9 KiB
C#
61 lines
1.9 KiB
C#
#nullable enable
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using System;
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using System.Collections.Concurrent;
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using System.Linq.Expressions;
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namespace T3.Core.Compilation;
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/// <summary>
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/// Just a helper class to create instances of T based on a type.
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/// Provides "constructors" (Func<T>) for types that are not known at runtime that are considerably faster than Activator.CreateInstance.
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/// </summary>
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/// <typeparam name="T">The type to create instances of</typeparam>
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public sealed class GenericFactory<T>
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{
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private readonly Type _defaultType;
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private readonly Type? _enumType;
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private readonly ConcurrentDictionary<Type, Func<T>> _entries = new();
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public GenericFactory(Type? defaultType, Type? enumType = null)
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{
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if(defaultType == null || !defaultType.IsAssignableTo(typeof(T)))
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throw new ArgumentException("defaultType must be a subclass of T", nameof(defaultType));
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_defaultType = defaultType;
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_enumType = enumType;
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}
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public T CreateFor(Type type)
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{
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if (_entries.TryGetValue(type, out var factory))
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{
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return factory();
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}
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factory = AddFactory(type, null);
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return factory();
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}
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public Func<T> AddFactory(Type type, Func<T>? constructor)
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{
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constructor ??= CreateFactoryFor(type);
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_entries[type] = constructor;
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return constructor;
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}
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private Func<T> CreateFactoryFor(Type type)
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{
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Type genericType;
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if(_enumType != null && type.IsEnum)
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{
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genericType = _enumType.MakeGenericType(type);
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}
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else
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{
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genericType = _defaultType.MakeGenericType(type);
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}
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var compiledConstructor = Expression.Lambda<Func<T>>(Expression.New(genericType)).Compile();
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return () => (T)compiledConstructor();
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}
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} |