在Swift中，有没有办法将数组元素分配给多个变量？

Question

我有一个像这样的长数组：

let array = [1, 2, 3]

我想像这样将所有元素的值分配给不同的变量：

var a, b, c:Int
[a, b, c] = array

我知道用元组是可能的，但我需要用数组来做，而不是单独做每个变量。

Answer 1

在可用的 list of patterns 中，没有“数组模式”或类似的东西，因此您不能对数组进行模式匹配。但是，您可以做的是：

let array = [1,2,3]
let (a, b, c) = (array[0], array[1], array[2])

如果数组少于 3 个元素，这将在运行时抛出错误。

Answer 2

它很有用，但不是内置的。非可变泛型让它变得很痛苦。

let (a, b, c) = [1, 2, 3].tuple3!

/// A workaround for not being able to extend tuples.
public struct Tuple<Elements> {
  public var elements: Elements

  public init(_ elements: Elements) {
    self.elements = elements
  }
}

public extension Tuple {
  // MARK: - 2-tuple

  /// Create a new tuple with one more element.
  static subscript<Element0, Element1, Element2>(
    tuple: Elements, element: Element2
  ) -> (Element0, Element1, Element2)
  where Elements == (Element0, Element1) {
    (tuple.0, tuple.1, element)
  }

  // MARK: - 3-tuple

  /// Create a new tuple with one more element.
  static subscript<Element0, Element1, Element2, Element3>(
    tuple: Elements, element: Element3
  ) -> (Element0, Element1, Element2, Element3)
  where Elements == (Element0, Element1, Element2) {
    (tuple.0, tuple.1, tuple.2, element)
  }
}

public extension Sequence {
  typealias Tuple2 = (Element, Element)
  typealias Tuple3 = (Element, Element, Element)
  typealias Tuple4 = (Element, Element, Element, Element)

  var tuple2: Tuple2? { makeTuple2()?.tuple }
  var tuple3: Tuple3? { makeTuple3()?.tuple }
  var tuple4: Tuple4? { makeTuple4()?.tuple }

  private func makeTuple2() -> (
    tuple: Tuple2,
    getNext: () -> Element?
  )? {
    var iterator = makeIterator()
    let getNext = { iterator.next() }

    guard
      let _0 = getNext(),
      let _1 = getNext()
    else { return nil }

    return ((_0, _1), getNext)
  }

  private func makeTuple3() -> (
    tuple: Tuple3,
    getNext: () -> Element?
  )? {
    guard
      let (tuple, getNext) = makeTuple2(),
      let element = getNext()
    else { return nil }

    return (Tuple[tuple, element], getNext)
  }

  private func makeTuple4() -> (
    tuple: Tuple4,
    getNext: () -> Element?
  )? {
    guard
      let (tuple, getNext) = makeTuple3(),
      let element = getNext()
    else { return nil }

    return (Tuple[tuple, element], getNext)
  }
}

在Swift中，有没有办法将数组元素分配给多个变量？

In Swift, is there a way to to assign elements of array to multiple variables?

arrays

variable-assignment

swift