重構 C# function 以降低其認知復雜性

Question

我從 SonarCube 收到以下錯誤：“重構此方法以將其認知復雜度從 28 降低到允許的 15”。 問題是，在認知復雜度如此高的情況下，我不知道如何將其降低到要求的 15 分。我曾嘗試將三個 if 語句移至不同的方法，但它僅將分數降低了 6 分。 我應該如何重構給定的代碼以滿足要求？

 [HttpGet]
        public IActionResult GetTileViewer(string productId = "", string edgeId = "", string sizeId = "", double? thickness = null)
        {
            if (string.IsNullOrWhiteSpace(productId))
            {
                return new ObjectResult(new { Error = "You need to specify a product id" })
                    { StatusCode = (int)HttpStatusCode.InternalServerError };
            }

            var commerceService = new CommerceService();
            var isImperial = commerceService.IsImperialMeasure();

            var id = 0;
            Guid guid;
            RockstarProductTile product = null;

            if (Guid.TryParse(productId, out guid))
            {
                product = ProductUtilities.GetProduct<RockstarProductTile>(guid);
            }
            else if (int.TryParse(productId, out id))
            {
                product = ProductUtilities.GetProduct<RockstarProductTile>(id);
            }

            if (product != null)
            {
                double? length = null;
                double? width = null;

                try
                {
                    if (!string.IsNullOrWhiteSpace(sizeId))
                    {
                        var split = sizeId.Split('-');
                        length = double.Parse(split[0]);
                        width = double.Parse(split[1]);
                    }

                    var variants = product.Variants
                        .Where(x => string.IsNullOrWhiteSpace(edgeId) || commerceService.GetRelatedEntries(x, CommerceAssociationGroups.Edge)
                            .Where(y => y.ContentLink.ID.ToString() == edgeId || y.ContentGuid.ToString() == edgeId).Any());

                    if (isImperial)
                    {
                        variants = variants
                            .Where(x => length == null || x.Rockstar_RockstarProductTileVariant_TileLengthInches == length || x.Rockstar_RockstarProductTileVariant_TileLengthFeet == length)
                            .Where(x => width == null || x.Rockstar_RockstarProductTileVariant_TileWidthInches == width || x.Rockstar_RockstarProductTileVariant_TileWidthFeet == width)
                            .Where(x => thickness == null || x.Rockstar_RockstarProductTileVariant_TileThicknessInches == thickness || x.Rockstar_RockstarProductTileVariant_TileThicknessFeet == thickness);
                    }
                    else
                    {
                        variants = variants
                            .Where(x => length == null || x.Rockstar_RockstarProductTileVariant_TileLengthInches == length)
                            .Where(x => width == null || x.Rockstar_RockstarProductTileVariant_TileWidthInches == width)
                            .Where(x => thickness == null || x.Rockstar_RockstarProductTileVariant_TileThicknessInches == thickness);
                    }

                    var variant = variants.FirstOrDefault();

                    if (variant != null)
                    {
                        var tileViewer = commerceService.GetRelatedEntries(variant, CommerceAssociationGroups.TileViewer).FirstOrDefault() as RockstarTileViewer;
                        var images = tileViewer?.Rockstar_TileViewer_Images?.Items.Select(x => _urlUtilities.GetRelativeUrl(x.ContentLink)).ToList();

                        var tempId = 0;
                        Guid tempGuid;
                        RockstarProductEdge edge = null;

                        if (Guid.TryParse(edgeId, out tempGuid))
                        {
                            edge = ProductUtilities.GetProduct<RockstarProductEdge>(tempGuid);
                        }
                        else if (int.TryParse(edgeId, out tempId))
                        {
                            edge = ProductUtilities.GetProduct<RockstarProductEdge>(tempId);
                        }

                        if (images != null)
                        {
                            return new JsonResult(new TileViewerDataObject { Label = edge?.Rockstar_RockstarProductEdge_EdgeName?.SupAndSubOnly() ?? product.DisplayName, Images = images });
                        }

                        return new JsonResult(new TileViewerDataObject { Label = edge?.Rockstar_RockstarProductEdge_EdgeName?.SupAndSubOnly() ?? product.DisplayName });
                    }
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex, "Error during get tile viewer: {Message}", ex.Message);
                }
            }

            return new JsonResult(new TileViewerDataObject());
        }

Answer 1

AFAIK 對認知復雜性的最大貢獻者是嵌套表達式，因此請嘗試減少嵌套。 例如， if - 從if (product != null)反轉為：

if (product == null)
{
    return new JsonResult(new TileViewerDataObject());
}

double? length = null; // also can be moved into the try block, not needed here
double? width = null;// also can be moved into the try block, not needed here

try
{
   ...
}
...

然后應該將獲取產品移至單獨的方法（在相當長的一段時間內，您可以將變量聲明內聯為id和guid等out變量）：

private RockstarProductTile GetProduct(string productId)
{
    RockstarProductTile result = null;
    if (Guid.TryParse(productId, out var guid))
    {
        product = ProductUtilities.GetProduct<RockstarProductTile>(guid);
    }
    else if (int.TryParse(productId, out var id))
    {
        product = ProductUtilities.GetProduct<RockstarProductTile>(id);
    }
    return result;
}

在方法體中調用它：

RockstarProductTile product = GetProduct(productId);

然后將相同的方法應用於try主體（也可能移動到單獨的方法） - 嘗試至少反轉一些if （ if (variant != null)是一個很好的候選者）並通過edgeId將獲取edge移動到單獨的方法中.

還嘗試使方法少於一個屏幕（通過將其分解為較小的屏幕，發現變體也可以移動到單獨的 function ）。