swift - 如何在 Swift 4.1 中从字典中随机选择三个元素

Question

我在从字典中挑选三个随机元素时遇到问题。

我的字典代码:

query.observeSingleEvent(of: .value, with: { snapshot in
    for child in snapshot.children {
        let childSnap = child as! DataSnapshot
        var dict = childSnap.value as! [String: Any]
    }
})

Answer 1

如果键是整数，则可以使用数组。

如果您只想使用字典，那么下面提到的代码可能对您有帮助

var namesOfPeople = [Int: String]()
namesOfPeople[1] = "jacob"
namesOfPeople[2] = "peter"
namesOfPeople[3] = "sam"

func makeList(n: Int) -> [Int] {
    print(namesOfPeopleCount)
    return (0..<n).map { _ in namesOfPeople.keys.randomElement()! }
}

let randomKeys = makeList(3)

您可以在旧版本的 Swift 中尝试此操作，其中 randomElement() 不可用

let namesOfPeopleCount = namesOfPeople.count
func makeList(n: Int) -> [Int] {
  return (0..<n).map{ _ in Int(arc4random_uniform(namesOfPeopleCount)
}