ios - 检查类型并转换为具体类型以进行功能签名

Question

我有以下代码，感觉可以改进。具体来说，我想摆脱转换和强制转换。多边形具有以下类型签名:
let polygon: MKShape & MKGeoJSONObject

switch polygon {
case is MKMultiPolygon:
    let multiPoly = polygon as! MKMultiPolygon
    renderer = MKMultiPolygonRenderer(multiPolygon: multiPoly)
case is MKPolygon:
    let polygon = polygon as! MKPolygon
    renderer = MKPolygonRenderer(polygon: polygon)
default:
    fatalError("Should have had a renderer")
}

Answer 1

您应该保持切换方法，并使用case let将对象转换为适当的类型:

switch polygon {
case let object as MKMultiPolygon:
    renderer = MKMultiPolygonRenderer(multiPolygon: object)
case let object as MKPolygon:
    renderer = MKPolygonRenderer(polygon: object)
default:
    fatalError("Should have had a renderer")
}