Swift数组按属性排序错误：实例方法“ localizedCaseInsensitiveCompare”要求使用“字符串？”符合'StringProtocol'

Question

我正在尝试对自定义对象的数组进行排序，但出现以下错误：

实例方法“ localizedCaseInsensitiveCompare”要求 '串？'符合“ StringProtocol”

filteredCountriesAndCities?.sorted(by: {$0.countryName?.localizedCaseInsensitiveCompare($1.countryName) == ComparisonResult.orderedAscending})

Answer 1

您需要处理countryName为nil的情况，这是最后对nil值进行排序的示例

let sorted = array.sorted {
    guard let first = $0.countryName else {
        return false
    }
    guard let second = $1.countryName else {
        return true
    }

    return first.localizedCaseInsensitiveCompare(second) == ComparisonResult.orderedAscending
}