Swift Array 按属性排序错误：实例方法“localizedCaseInsensitiveCompare”需要“String?” 符合 'StringProtocol'

Question

我正在尝试对这个自定义对象数组进行排序，但出现以下错误：

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

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

Answer 1

您需要处理countryName为 nil 的情况，这里是一个最后排序 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
}