ios - NSSortDescriptor 比 swift 高阶函数有什么优势？

Question

下面是 NSSortDescriptor 的使用示例，它给出与 sortedByFirstNameSwifty 相同的结果，那么在 Swift 中需要什么 NSSortDescriptor ？

class Person: NSObject {
    let firstName: String
    let lastName: String
    let age: Int

    init(firstName: String, lastName: String, age: Int) {
        self.firstName = firstName
        self.lastName = lastName
        self.age = age
    }
    override var description: String {
        return "\(firstName) \(lastName)"
    }
 }

let a = Person(firstName: "a", lastName: "b", age: 24)
let b = Person(firstName: "c", lastName: "d", age: 27)
let c = Person(firstName: "e", lastName: "f", age: 33)
let d = Person(firstName: "g", lastName: "h", age: 31)
let peopleObject = [d, b, a, c]
//SWIFTY
let sortedByFirstNameSwifty =  peopleObject.sorted(by: { $0.firstName < $1.firstName })
print(sortedByFirstNameSwifty)//prints[a b, c d, e f, g h]


//Objective c way
let firstNameSortDescriptor = NSSortDescriptor(key: "firstName", ascending: true, selector: #selector(NSString.localizedStandardCompare(_:)))
let sortedByFirstName = (peopleObject as NSArray).sortedArray(using: [firstNameSortDescriptor])
print(sortedByFirstName)//prints [a b, c d, e f, g h]

Answer 1

NSSortDescriptor 的优点是您可以使用它们的数组进行排序，如果根据第一个描述符结果两个对象相等，您可以回退到第二个描述符来对它们进行排序。

例如，假设您要按修改日期对多个文件进行排序。如果两个文件碰巧具有完全相同的修改日期，您可能希望改为按名称对这两个文件进行排序。因此，您将使用一个排序描述符数组，第一个按日期排序，第二个按文件名排序。