For Apple in Apple Swift

Question

Apple最新发布的语言Swift在官方文档中有一个例子.例子是这样的;

let interestingNumbers = [
    "Prime": [2, 3, 5, 7, 11, 13],
    "Fibonacci": [1, 1, 2, 3, 5, 8],
    "Square": [1, 4, 9, 16, 25],
]
var largest = 0
for (kind, numbers) in interestingNumbers {
    for number in numbers {
        if number > largest {
            largest = number
        }
    }
}
largest

这很简单,但作为额外的练习,它需要添加另一个变量以返回最大数字的类型(即Square就是这里的情况)

但是,我似乎无法弄清楚这里的"(种类,数字)"是什么,我应该如何使我的for循环遍历所有Dictionary(interestingNumbers)键并找到哪个键具有最大数字.

谢谢大家的帮助

Answer 1

Swift允许您使用元组语法 循环字典(key, value).因此,在for循环的每次迭代中,Swift关心将指定的元组变量(kind以及number在您的情况下)重新分配给实际的字典记录.

要确定哪个Key包含示例中的最大数字,您可以按如下方式扩展代码:

let interestingNumbers = [
    "Prime": [2, 3, 5, 7, 11, 13],
    "Fibonacci": [1, 1, 2, 3, 5, 8],
    "Square": [1, 4, 9, 16, 25],
]

var largest = 0
var largestKey = ""
for (kind, numbers) in interestingNumbers {
    for number in numbers {
        if number > largest {
            largest = number
            largestKey = kind
        }
    }
}
largest     // =25
largestKey  // ="Square"

或者,如果您想练习元组语法,请尝试(具有相同的结果):

var largest = 0
var largestKey = ""
for (kind, numbers) in interestingNumbers {
    for number in numbers {
        if number > largest {
            (largestKey, largest) = (kind, number)
        }
    }
}
largest     // =25
largestKey  // ="Square"