ios - 如何在 Swift 中将字典值数组打印成漂亮的字符串

Question

我有一组 routine 对象，它们被定义为:

struct Routine {
    let routineName: String
    let routineExercisesAndSets: [String: Int]
}

let routines: [Routine] = {
    let firstRoutine = Routine(routineName: "Legs", routineExercisesAndSets: ["Squats":4,"Lunges":4,"Calf Raises":4])

    let secondRoutine = Routine(routineName: "Chest", routineExercisesAndSets: ["Bench Press":4,"Press Ups":4,"Flyes":4,"Inclined Bench Press":4])

    let thirdRoutine = Routine(routineName: "Arms", routineExercisesAndSets: ["Bicep Curls":4,"Hammer Curls":4,"Preacher Curls":4,"Tricep Extension":4,"Tricep Dips":4])

    return [firstRoutine, secondRoutine, thirdRoutine]
}()

我正在尝试将它们返回 routineExercisesAndSets 数组作为详细文本，并在使用 array.description 函数时在 tableView 中得到此结果

我的问题是，我如何遍历例程对象并打印出看起来像这样的“漂亮”格式化字符串:

“小腿抬高 x 4，深蹲 x 4，弓步 x 4...”

我可以使用以下代码在新行上打印出单独的键值对:

for i in routines{
    for (key, value) in (i.routineExercisesAndSets)! {
        print("\(key) x \(String(value))")
    }
}

产生:

小腿抬高 x 4
深蹲 x 4
弓步 x 4
卧推 x 4
俯卧撑 x 4
苍蝇 x 4
上斜卧推 x 4
三头肌拉伸(stretch) x 4
三头肌浸入 x 4
传教士卷发 x 4
锤式弯举 x 4
二头肌 curl x 4

但我想按它们的父对象对它们进行分组，这样例程的练习就会显示在同一行上，因此它看起来像示例 “Calf Raises x 4, Squats x 4, Lunges x 4...” 。

Answer 1

您可以使用链式 map 和 joined 操作来构造单个 String 来描述给定练习的练习字典。例如

for routine in routines {
    print("Routine:", routine.routineName)
    print("--------------")
    print(routine.routineExercisesAndSets
        .map { $0 + " x \($1)" }
        .joined(separator: ", "))
    print()
}
/* Routine: Legs
   --------------
   Calf Raises x 4, Squats x 4, Lunges x 4

   Routine: Chest
   --------------
   Bench Press x 4, Press Ups x 4, Flyes x 4, Inclined Bench Press x 4

   Routine: Arms
   --------------
   Tricep Extension x 4, Tricep Dips x 4, Preacher Curls x 4, Hammer Curls x 4, Bicep Curls x 4 

                   */

此外，您可以将它们实现为 Routine 的计算 description 属性的返回，而不是在每次使用时显式执行这些“表示”转换，作为一部分让 Routine 符合 CustomStringConvertible :

extension Routine: CustomStringConvertible {
    var description: String {
        return routineName + ":\n" + routineExercisesAndSets
            .map { $0 + " x \($1)" }
            .joined(separator: ", ")
    }
}

for routine in routines {
    print(routine) /* uses Routine:s implementation of 'CustomStringConvertible',
                      the computed property 'description`, specifically           */
    print()
}
/* Legs:
   Calf Raises x 4, Squats x 4, Lunges x 4

   Chest:
   Bench Press x 4, Press Ups x 4, Flyes x 4, Inclined Bench Press x 4

   Arms:
   Tricep Extension x 4, Tricep Dips x 4, Preacher Curls x 4, Hammer Curls x 4, Bicep Curls x 4

                   */

---

鉴于您在下面的评论，似乎 Routine 的属性 routineName 和 routineExercisesAndSets 是可选的。如果是这种情况，您自然需要在访问它们的(可能存在的)值之前处理它们的解包。例如，如果两个属性中的任何一个为 nil，则返回一个空的 description，否则返回组合的例程名称和详细描述(如上面非可选示例中所做的) :

struct Routine {
    let routineName: String?
    let routineExercisesAndSets: [String: Int]?
}

extension Routine: CustomStringConvertible {
    var description: String {
        guard let name = routineName, let details = routineExercisesAndSets else { return "" }
        return name + ":\n" + details.map { $0 + " x \($1)" }.joined(separator: ", ")
    }
}