將不同型別的Action<T>陣列傳遞給方法

我有以下代碼，它根據作為引數傳遞的值的型別存盤要執行的操作串列...

Action<int> intAction = x => Console.WriteLine($"You sent an int: {x}");
Action<bool> boolAction = x => Console.WriteLine($"You sent a bool: {x}");

var funcsByInputType = new Dictionary<Type, Action<object>>();
funcsByInputType[typeof(int)] = (object x) => intAction((int)x);
funcsByInputType[typeof(bool)] = (object x) => boolAction((bool)x);

PerformAction(true);
PerformAction(42);

void PerformAction<TValue>(TValue value)
{
    if (funcsByInputType!.TryGetValue(typeof(TValue), out Action<object>? action))
    {
        action(value!);
    }
}

這按預期作業。

我現在想做的是從一個我只呼叫一次的方法創建字典，所以我可以像這樣重寫我的代碼。

Action<int> intAction = x => Console.WriteLine($"You sent an int: {x}");
Action<bool> boolAction = x => Console.WriteLine($"You sent a bool: {x}");

funcsByInputType = MakeFuncsByInputType(intAction, boolAction);

PerformAction(true);
PerformAction(42);

void PerformAction<TValue>(TValue value)
{
    if (funcsByInputType!.TryGetValue(typeof(TValue), out Action<object>? action))
    {
        action(value!);
    }
}

我怎么能寫MakeFuncsByInputType方法？

請注意，我不想多次呼叫該方法，也不想將我的引數定義為params object[]

uj5u.com熱心網友回復：

這是不可能的，因為通過 anAction<object>作為別名Action<string>I 將能夠傳遞42而不是字串。

所以我不得不改用構建器模式。

public static partial class Reducer { public static Builder New() => new Builder();

public class Builder<TState>
{
    private bool Built;
    private ImmutableArray<KeyValuePair<Type, Func<TState, object, Result<TState>>>> TypesAndReducers;

    internal Builder() => TypesAndReducers = ImmutableArray.Create<KeyValuePair<Type, Func<TState, object, Result<TState>>>>();

    public Builder<TState> Add<TDelta>(Func<TState, TDelta, Result<TState>> reducer)
    {
        if (reducer is null)
            throw new ArgumentNullException(nameof(reducer));

        EnsureNotBuilt();
        TypesAndReducers = TypesAndReducers.Add(new(typeof(TDelta), (state, delta) => reducer(state, (TDelta)delta)));
        return this;
    }

    public Func<TState, object, Result<TState>> Build()
    {
        EnsureNotBuilt();
        if (TypesAndReducers.Length == 0)
            throw new InvalidOperationException("Must add at least one reducer to build.");

        Built = true;

        var dictionary = TypesAndReducers
            .GroupBy(x => x.Key)
            .ToDictionary(x => x.Key, x => x.Select(x => x.Value));

        return (TState state, object delta) =>
        {
            if (delta is null)
                throw new ArgumentNullException(nameof(delta));

            if (!dictionary.TryGetValue(delta.GetType(), out var reducers))
                return (false, state);

            bool anyChanged = false;
            TState newState = state;
            foreach(var reducer in reducers)
            {
                (bool changed, newState) = reducer(newState, delta);
                anyChanged |= changed;
            }

            return anyChanged
                ? (true, newState)
                : (false, state);
        };
    }

    private void EnsureNotBuilt()
    {
        if (Built)
            throw new InvalidOperationException("Reducer has already been built.");
    }

}

}

標籤：C＃ 仿制药

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