Swift 字典在不访问或不知道 key 的情况下获取值

Question

我正在使用字典并尝试在不知道或访问 key 的情况下获取值。我的字典看起来像 "Olivia":[2.0, 0.0, 1.0, 3.0],"Amber":[60.0, 0.0, 0.0, 1.0] 它是一个 [String: ArrayDouble ] 字典，但我想检查 Value(ArrayDouble) 中是否有包含 60.0 的任何值，然后显示该值的键。我试图做的是:

let number = 60.0
for (key, value) in dict{

  if (number== value[0]){

    print(...the key)

  }else{

}

Answer 1

你也可以使用first(_ where:),

let item = dict.first { key, value in
  value.contains(60)
}

let key = item?.key // this is your key Amber

有了这个，您可以创建一个谓词函数，您可以修改它以满足您的需要，

let predicate = { (num: Double) -> Bool in
  num == 60.0
}

let dict = ["Olivia":[2.0, 0.0, 1.0, 3.0],"Amber":[60.0, 0.0, 0.0, 1.0]]

let item = dict.first { key, value in
  value.contains(where: predicate)
}

item?.key

您可以根据需要更改谓词，

let predicate = {(num: Double) -> Bool in num > 60.0} // predicate to filter first key with values greater than 60.0

let predicate = {(num: Double) -> Bool in num < 60.0} // predicate to filter first key with values greater than 60.0

等等。