sort using key paths

sort

// ⭐️ custom sorting using key paths
extension Sequence {
    func sorted<T: Comparable>(
        by    keyPath: KeyPath<Element, T>,
        // ⭐️ in ascending order by default.
        using compare: (T, T) -> Bool = (<)    // ⭐️ 預設運算(括號為必要)
    ) -> [Element] {
        sorted { a, b in
            compare(a[keyPath: keyPath], b[keyPath: keyPath])
        }
    }
}

todolist.sorted(by: \.date)
todolist.sorted(by: \.item).map(\.item)
todolist.sorted(by: \.item, using: >).map(\.item)  // descending order

TodoItem

import Foundation  // Date

// todo item
struct TodoItem {
    let date: Date
    let item: String
}

// todo item samples
let todos = ["eat", "sleep", "play", "relax"]
let now = Date()
let nextyear = now.yearAfter

extension TodoItem {
    static let samples = (1...5).map{ _ in 
        TodoItem(
            date: .random(in: now...nextyear), 
            item: todos.randomElement()!
        )
    }
}

let todolist = TodoItem.samples

👥 相關

• Key Path

• seq.sorted(_:) ⭐️ - sort by multiple keypaths