未获取数组的最大元素

Question

我有一个名为prodIDArr的字符串数组，其值如下...

["1","2","3","4","5","6","7","8","9","10"] 

但是当我做这样的事情时..

let maxVal = prodIDArr.max()

我得到maxVal的值为 9 而不是 10。

这其中可能是什么原因...？

Answer 1

这是一个字符串数组，按字典顺序比较：

"1" < "10" < "2" < ... < "9" 

例如"10" < "2"因为初始字符已经 满足"1" < "2".(有关血腥细节，请参阅示例 Swift 中的字符串和字符比较不区分区域设置是什么意思？

使用整数数组将是最佳解决方案：

let prodIDArr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
let maxId = prodIDArr.max()
print(maxId) // Optional(10)

如果无法做到这一点，则可以强制执行数字比较

let prodIDArr = ["1","2","3","4","5","6","7","8","9","10"]
let maxId = prodIDArr.max(by: { $0.compare($1, options: .numeric) == .orderedAscending })
print(maxId) // Optional("10")

Answer 2

您还可以将原始字符串数组映射到 int 数组

let prodIDArr = ["1","2","3","4","5","6","7","8","9","10"]
let prodNumArray = prodIDArr.map { input in Int(input)!} // or { Int($0)! }
print(prodNumArray.max()!)