Question

我有2个词典：

let foo: [String: Any] = ["name": "John", "isHuman": true, "age": 20]
let bar: [String: Any] = ["name": "Ann", "isHuman": true, "age": 34]

我想在比较中排除某些键时进行比较。我想要排除的键位于另一个字典中：

let car: [String: Any] = ["age": 20]

我有这个扩展名：

extension Dictionary where Key: Equatable {
    func isEqualTo(_ dictionary: Dictionary, excluding: [Key] = []) -> Bool {
      let left = filter({ !excluding.contains($0.key) })
      let right = dictionary.filter({ !excluding.contains($0.key) })
      return NSDictionary(dictionary: left).isEqual(to: right)
    }
}

但是当我调用它时，我需要将排除的密钥包装在Array中，否则编译器将失败：

无法将“Dictionary.Keys”类型的值转换为预期的参数类型“[String]”

foo.isEqualTo(bar, excluding: Array(car.keys))有效。

foo.isEqualTo(bar, excluding: car.keys)会导致编译错误。

我是否可以调整我的扩展程序以避免将排除的密钥包装在Array中？

Answer 1

car.keys的类型为Dictionary<Key, Value>.Keys，即集合而不是数组。

如果您将该功能声明为

func isEqualTo<C: Collection>(_ dictionary: Dictionary, excluding: C) -> Bool
        where C.Element == Key

然后两者

foo.isEqualTo(bar, excluding: Array(car.keys))
foo.isEqualTo(bar, excluding: car.keys)

编译和工作。

Answer 2

将excluding声明为Keys类型。

func isEqualTo(_ dictionary: Dictionary, excluding: Keys = [:].keys) -> Bool {

作为旁注，您可以通过将代码更新为：

来消除NSDictionary的使用

let foo: [String: AnyHashable] = ["name": "John", "isHuman": true, "age": 20]
let bar: [String: AnyHashable] = ["name": "Ann", "isHuman": true, "age": 34]

let car: [String: Any] = ["age": 20, "name":"Bob"]

extension Dictionary where Key: Equatable, Value: Equatable {
    func isEqualTo(_ dictionary: Dictionary, excluding: Keys = [:].keys) -> Bool {
        let left = filter({ !excluding.contains($0.key) })
        let right = dictionary.filter({ !excluding.contains($0.key) })
        return left == right
    }
}

请注意使用AnyHashable代替Any字段，并注意扩展中添加的, Value: Equatable。

比较字典，同时排除某些键

2 个答案: