如何在解析文件中的两个不同对象时避免重复代码？

Question

我想解析一个如下所示的 csv 文件。 CSV 文件包含两种不同的类型：行星和小行星。这两种类型都有一些独特的属性。

我创建了一个 Planet 类和一个 Asteroid 类，它们都继承自抽象 SpaceObject 类。我创建了一个解析器类，它将我的 csv 文件解析为一个 SpaceObjects 列表。不幸的是，我的课程包含重复的代码，而这正是我要避免的。

我的代码：

switch (ReadStringFromCellBasedOnHeader("type"))
{
    case "Asteroid":
        var asteroid = new Asteroid();
        asteroid.Position = new Vector2D(ReadDoubleFromCellBasedOnHeader("x"), ReadDoubleFromCellBasedOnHeader("y"));
        asteroid.Speed = new Vector2D(ReadDoubleFromCellBasedOnHeader("vx"), ReadDoubleFromCellBasedOnHeader("vy"));
        asteroid.Radius = ReadDoubleFromCellBasedOnHeader("radius");
        asteroid.Color =
            (Color?)ColorConverter.ConvertFromString(ReadStringFromCellBasedOnHeader("color")) ?? Color.FromRgb(0, 0, 0);
        break;
    case "Planet":
        var planet = new Planet();
        planet.Name = ReadStringFromCellBasedOnHeader("name");
        planet.Position = new Vector2D(ReadDoubleFromCellBasedOnHeader("x"), ReadDoubleFromCellBasedOnHeader("y"));
        planet.Speed = new Vector2D(ReadDoubleFromCellBasedOnHeader("vx"), ReadDoubleFromCellBasedOnHeader("vy"));
        planet.Neighbours.AddRange(ReadStringFromCellBasedOnHeader("neighbours").Split(','));
        planet.Radius = ReadDoubleFromCellBasedOnHeader("radius");
        planet.Color =
            (Color?)ColorConverter.ConvertFromString(ReadStringFromCellBasedOnHeader("color")) ?? Color.FromRgb(0, 0, 0);
        break;
    default:
        throw new Exception("Unknown SpaceObject Type");
}

string ReadStringFromCellBasedOnHeader(string header)
{
    return fields[columnDictionary[header]];
}

double ReadDoubleFromCellBasedOnHeader(string header)
{
    return StringConverter.ToDouble(ReadStringFromCellBasedOnHeader(header));
}

正如您所见，我的 Planet 和 Asteroid 对象完全相同，除了 Planet 包含两个独特的属性（名称和邻居）。我在考虑使用 Factory 或 Builder 模式，但我不想创建一个有九个参数的函数。如何以优雅的方式避免重复代码？

Answer 1

你可以简单地把它们放在开关下面：

SpaceObject spaceObject;

switch (ReadStringFromCellBasedOnHeader("type"))
{
    case "Asteroid":
        spaceObject = new Asteroid();
        break;
    case "Planet":
        var planet = new Planet();
        spaceObject = planet;
        planet.Name = ReadStringFromCellBasedOnHeader("name");
        planet.Neighbours.AddRange(ReadStringFromCellBasedOnHeader("neighbours").Split(','));
        break;
    default:
        throw new Exception("Unknown SpaceObject Type");
}

spaceObject.Position = new Vector2D(ReadDoubleFromCellBasedOnHeader("x"), ReadDoubleFromCellBasedOnHeader("y"));
spaceObject.Speed = new Vector2D(ReadDoubleFromCellBasedOnHeader("vx"), ReadDoubleFromCellBasedOnHeader("vy"));
spaceObject.Radius = ReadDoubleFromCellBasedOnHeader("radius");
spaceObject.Color =
    (Color?)ColorConverter.ConvertFromString(ReadStringFromCellBasedOnHeader("color")) ?? Color.FromRgb(0, 0, 0);

或者，您可以使用辅助函数：

switch (ReadStringFromCellBasedOnHeader("type"))
{
    case "Asteroid":
        var asteroid = new Asteroid();
        DeserializeCommon(asteroid);
        break;
    case "Planet":
        var planet = new Planet();
        DeserializeCommon(planet);
        planet.Name = ReadStringFromCellBasedOnHeader("name");
        planet.Neighbours.AddRange(ReadStringFromCellBasedOnHeader("neighbours").Split(','));
        break;
    default:
        throw new Exception("Unknown SpaceObject Type");
}

void DeserializeCommon(SpaceObject spaceObject)
{
    spaceObject.Position = new Vector2D(ReadDoubleFromCellBasedOnHeader("x"), ReadDoubleFromCellBasedOnHeader("y"));
    spaceObject.Speed = new Vector2D(ReadDoubleFromCellBasedOnHeader("vx"), ReadDoubleFromCellBasedOnHeader("vy"));
    spaceObject.Radius = ReadDoubleFromCellBasedOnHeader("radius");
    spaceObject.Color =
        (Color?)ColorConverter.ConvertFromString(ReadStringFromCellBasedOnHeader("color")) ?? Color.FromRgb(0, 0, 0);.
}

Answer 2

通过将重复的代码移到开关外：

SpaceObject spaceObject;
switch (ReadStringFromCellBasedOnHeader("type"))
{
    case "Asteroid":
        spaceObject = new Asteroid();
        break;
    case "Planet":
        var planet = new Planet()
        {
            Name = ReadStringFromCellBasedOnHeader("name"),
            Neighbours = new List<string>();    
        };
        planet.Neighbours.AddRange(
             ReadStringFromCellBasedOnHeader("neighbours").Split(','));
        spaceObject = planet;
        break;
    default:
        throw new Exception("Unknown SpaceObject Type");
}
spaceObject.Position = new Vector2D(ReadDoubleFromCellBasedOnHeader("x"), ReadDoubleFromCellBasedOnHeader("y"));
spaceObject.Speed = new Vector2D(ReadDoubleFromCellBasedOnHeader("vx"),ReadDoubleFromCellBasedOnHeader("vy"));
spaceObject.Radius = ReadDoubleFromCellBasedOnHeader("radius");
spaceObject.Color =
    (Color?) ColorConverter.ConvertFromString(ReadStringFromCellBasedOnHeader("color")) ?? Color.FromRgb(0, 0, 0);