arrays - 无法在 Array Extension Swift 上从自身调用函数

Question

我正在扩展 Array快速上课。我需要对数组进行排序，但是当我尝试这样做时，出现错误 Immutable value of type 'Array<T>' only has mutating members named 'sort'

这是我的扩展:

import UIKit

extension Array {

    func sortedArrayByTimeUsingKey(key: String, ascending: Bool) {

        sort { (firstObject, secondObject) -> Bool in

            let firstDict = firstObject as [String: AnyObject]
            let secondDict = secondObject as [String: AnyObject]

            let firstDateString = firstDict[key]! as String
            let secondDateString = secondDict[key]! as String

            let dateFormatter = DateFormatter()

            let firstDate = dateFormatter.dateFromString(firstDateString)!
            let secondDate = dateFormatter.dateFromString(secondDateString)!

            let order = firstDate.compare(secondDate)

            switch order {
            case .OrderedAscending:
                return ascending ? true : false
            case .OrderedDescending:
                return ascending ? true : false
            default:
                return true
            }
        }
    }

}

我怎么投 self是可变的，或者我如何检查 self是可变的吗？

Answer 1

如果该方法修改了实例本身，则该方法必须是可变的。所以只需在 func 之前添加 mutating 关键字即可。