arrays - 对排除 Nil 的数组进行排序

Question

我正在尝试对包含零变量的数组进行排序。

class TestArray {
    var a: String? = nil
    var b: String? = nil
    init(a: String?, b: String?) {
        self.a = a
        self.b = b
    }
}

let first = TestArray(a: "xxx", b: "yyy")
let second = TestArray(a: "zzz", b: "zzz")
let third = TestArray(a: "aaa", b: nil)

var array = [first, second, third]
array.sort(by: {($0.a as String!) > ($1.a as String!)})

array.sort(by: {($0.b as String!) > ($1.b as String!)}) // Throws an error

如何按 b 排序并在数组末尾留下 b = nil 的第三个 TestArray？此外，我想对所有 b 进行排序，然后对 b = nil 的数组按 a 对剩余的进行排序。

Answer 1

我相信这应该涵盖您想要的情况，而无需多次迭代(这是昂贵的)

array.sort { (lessThan, item) -> Bool in

    switch (lessThan.a, lessThan.b, item.a, item.b) {
    // if bs exist, use that comparison
    case (_, .some(let lessThanB), _, .some(let itemB)):
        return lessThanB < itemB
    // if bs don't exist by as do, use that comparison
    case (.some(let lessThanA), .none, .some(let itemA), .none):
        return lessThanA < itemA
    // if one item has a value but the other doesn't, the item with the value should be first
    case (_, .some(_), _, .none), (.some(_), _, .none, _ ):
        return true

    default:
        return false
    }
}