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我只是转换为雨燕4,我现在得到以下错误: 无法下标类型“String.UnicodeScalarView”的值和类型“CountableRange”(又名“CountableRange”)字符串下标错误
的索引代码行如下:
extension AppInvite.PromoCode {
fileprivate static func truncate(string: String) -> String {
let validCharacters = CharacterSet.alphanumerics
let cleaned = string.unicodeScalars.filter {
validCharacters.contains(UnicodeScalar(UInt16($0.value))!)
}
let range = 0 ..< min(10, cleaned.count)
let characters = cleaned[range].map(Character.init)
return String(characters)
}
}
我该如何纠正它?