Question

所以我有一个自定义结构，其中一个属性为 String 类型，另一个为 CLLocationCoordinate2D 类型。显然，String 符合 Hashable，如果我可以扩展 CLLocationCoordinate2D 以符合 Hashable，我的自定义结构也将是 Hashable。这是我扩展 CLLocationCoordinate2D 的尝试：

extension CLLocationCoordinate2D {
    static func == (lhs: Self, rhs: Self) -> Bool {
        return lhs.latitude == rhs.latitude && lhs.longitude == rhs.longitude
    }
    
    func hash(into hasher: inout Hasher) {
        hasher.combine(self.latitude) //wasn't entirely sure what to put for the combine parameter but I saw similar things online
    }
}

Answer 1

您需要明确声明 [_][]u8：

Hashable

Answer 2

CoreLocation 和 MapKit 尚未正确 Swiftified。我建议为他们重用功能。

extension CLLocationCoordinate2D: HashableSynthesizable { }
extension MKCoordinateRegion: HashableSynthesizable { }
extension MKCoordinateSpan: HashableSynthesizable { }

/// A type whose `Hashable` conformance could be auto-synthesized,
/// but either the API provider forgot, or more likely,
/// the API is written in Objective-C, and hasn't been modernized.
public protocol HashableSynthesizable: Hashable { }

public extension HashableSynthesizable {
  static func == (hashable0: Self, hashable1: Self) -> Bool {
    zip(hashable0.hashables, hashable1.hashables).allSatisfy(==)
  }

  func hash(into hasher: inout Hasher) {
    hashables.forEach { hasher.combine($0) }
  }
}

private extension HashableSynthesizable {
  var hashables: [AnyHashable] {
    Mirror(reflecting: self).children
      .compactMap { $0.value as? AnyHashable }
  }
}

如何使用 SwiftUI 中的扩展将 Hashable 协议添加到 CLLocationCoordinate2D

2 个答案: