C＃泛型+多態性解決方法？

Question

因此，我目前有一些包裝Unity WWW類的方法。 HandleTexture，HandleText，HandleBytes ...，但這是很多復制粘貼的浪費。 我試圖將其全部包裝在一個通用的HandleResult方法下，該方法將事情交給幕后的_HandleResult。 在這一點上，C＃編譯器抱怨無法將T靜態地鍵入到Texture（帶有closure(...);每一行closure(...);

private IEnumerator _HandleResult<T> (System.Action<T> closure, System.Action<string> onError){
    yield return webRequest;

    // Can't do a switch statement on Type, needs to be if/else chain :(
    if (SuccessWithoutErrors(onError)) {
        if(typeof(T) == typeof(Texture))
            closure(webRequest.texture);
        else if(typeof(T) == typeof(string))
            closure(webRequest.text);
        else if(typeof(T) == typeof(MovieTexture))
            closure(webRequest.movie);
        else if(typeof(T) == typeof(byte[]))
            closure(webRequest.bytes);
        else
            throw new System.NotSupportedException("Could not interpret response data as " + typeof(T).Name + ". Supported types include Texture, MovieTexture, byte[] and string.");
    }
}

我已經在這一點上停留了一段時間。 我對C＃相當陌生，所以也許我想要的根本不可行。 非常感謝來自對類型系統有更多了解的人的輸入，或者為減少重復代碼，我應該尋求哪些替代品以實現相同的效果。

Answer 1

如果直接轉換為泛型類型，C＃似乎不喜歡它。 但是您可以先轉換為object ，然后轉換為通用類型：

private IEnumerator _HandleResult<T> (System.Action<T> closure, System.Action<string> onError){
    yield return webRequest;

    if (SuccessWithoutErrors(onError)) {
        if(typeof(T) == typeof(Texture))
            closure((T)(object)webRequest.texture);
        else if(typeof(T) == typeof(string))
            closure((T)(object)webRequest.text);
        else if(typeof(T) == typeof(MovieTexture))
            closure((T)(object)webRequest.movie);
        else if(typeof(T) == typeof(byte[]))
            closure((T)(object)webRequest.bytes);
        else
            throw new System.NotSupportedException("Could not interpret response data as " + typeof(T).Name + ". Supported types include Texture, MovieTexture, byte[] and string.");
    }
}

---

較干凈的選項可能是提供執行屬性選擇的功能：

private IEnumerator _HandleResult<T> (System.Action<T> closure, Func<WebRequest, T> selector, System.Action<string> onError){
    yield return webRequest;

    if (SuccessWithoutErrors(onError)) { 
        closure(selector(webRequest)); 
    }
}

然后，您可以擁有一個函數簽名並調用以下站點：

void DoSomethingWithTexture(Texture t) {}

_HandleResult<Texture>(DoSomethingWithTexture, wr => wr.Texture, onError);

第二種方法更干凈，更靈活（如果以后要向要處理的對象添加Texture2屬性，該怎么辦？）但是需要更改API，並且可能更難以在現有代碼中實現。

Answer 2

嘗試這個：

    private IEnumerator _HandleResult<T>(object closure, System.Action<string> onError)
    {
        yield return webRequest;

        // Can't do a switch statement on Type, needs to be if/else chain :(
        if (true)
        {
            if (typeof(T) == typeof(Texture))
                ((System.Action<Texture>)closure)(webRequest.texture);
            else if (typeof(T) == typeof(string))
                ((System.Action<string>)closure)(webRequest.text);
            else if (typeof(T) == typeof(MovieTexture))
                ((System.Action<MovieTexture>)closure)(webRequest.movie);
            else if (typeof(T) == typeof(byte[]))
                ((System.Action<byte[]>)closure)(webRequest.bytes);
            else
                throw new System.NotSupportedException("Could not interpret response data as " + typeof(T).Name + ". Supported types include Texture, MovieTexture, byte[] and string.");
        }
    }