Swift Array 按屬性排序錯誤：實例方法“localizedCaseInsensitiveCompare”需要“String?” 符合 'StringProtocol'

Question

我正在嘗試對這個自定義對象數組進行排序，但出現以下錯誤：

實例方法“localizedCaseInsensitiveCompare”需要“String?” 符合 'StringProtocol'

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

Answer 1

您需要處理countryName為 nil 的情況，這里是一個最后排序 nil 值的示例

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
}