multi_sort.swift

struct Entity {
    let name: String
    let age: Int
}

enum SortResult {
    case LeftFirst
    case RightFirst
    case Same
}

func multiSort<T>(array: [T], sorter: [(T, T) -> SortResult]) -> [T] {
    return sorted(array, { (a, b) -> Bool in
        var r: SortResult?
        for cb in sorter {
            r = cb(a, b)
            if r != .Same {
                break
            }
        }
        return r == .LeftFirst ? true : false
    })
}

var arr = [
    Entity(name: "b", age: 18),
    Entity(name: "a", age: 18),
    Entity(name: "c", age: 20),
    Entity(name: "d", age: 30)
]

var r = multiSort(arr, [
    {(a, b) in a.age == b.age ? .Same : (a.age < b.age ? .LeftFirst : .RightFirst)},
    {(a, b) in a.name < b.name ? .LeftFirst : .RightFirst},
])