如何解决 Apple 的 App Development With Swift iBook 中的第 2.2 课实验？

Question

我是一个尝试使用 Apple 的 "App Development With Swift" iBook 学习 swift 的菜鸟，但似乎无法完成第 2.2 课“函数”中的最终实验。谁能指导我以正确的方式完成实验？以下是实验室的要求：现在编写一个名为 pacing 的函数，该函数采用四个双精度参数，分别称为 currentDistance、totalDistance、currentTime 和 goalTime。该函数还应该 return 一个字符串，这将是向用户显示的消息。该函数应调用 calculatePace，传入适当的值，并捕获 return 值。然后，该函数应将 returned 值与 goalTime 进行比较，如果用户处于节奏 return "Keep it up!"，否则 return "You've got to push it a bit harder!"。调用函数并打印 return 值。

这是我之前在实验室不同部分的 calculatePace 函数：

func calculatePace(currentDistance: Double, totalDistance: Double, currentTime: Double) -> Double {
    let currentSpeed = currentDistance / currentTime
    return ((totalDistance / currentSpeed) / 60)
}
print("\(calculatePace(currentDistance: 1, totalDistance: 10, currentTime: 6)) hours till you finish the run!")

这是我试图用来解决实验室问题但遇到问题的功能：

func pacing(currentDistance: Double, totalDistance: Double, currentTime: Double, goalTime: Double) -> String {
    //I don't know what to put in return
    return ("test return")
    calculatePace(currentDistance: 1, totalDistance: 10, currentTime: 6, goalTime: 60)
}
pacing(currentDistance: 1, totalDistance: 10, currentTime: 6, goalTime: 60)

我不明白我应该如何捕获 return 值，实验室的最后几句话让我很困惑。 "And if the user is on pace return "坚持下去！”，否则 return "You've got to push it just a bit harder!"。调用函数并打印 return 值。”这两个不同的印刷品不是吗，所以我如何 return 两者以及其他部分是什么意思？

Answer 1

我想这就是你想要的，请检查..

 func calculatePace(currentDistance: Double, totalDistance: Double, currentTime: Double) -> Double {
        let currentSpeed = currentDistance / currentTime
        return (totalDistance / currentSpeed)
 }
 print("\(calculatePace(currentDistance: 1, totalDistance: 10, currentTime: 6)) hours till you finish the run!")

 func pacing(currentDistance: Double, totalDistance: Double, currentTime: Double, goalTime: Double) -> String {
        let yourFinishTime = calculatePace(currentDistance: currentDistance, totalDistance: currentDistance, currentTime: currentTime)
        var message = ""

        if yourFinishTime > goalTime {
            message = "You've got to push it a bit harder!"
        }else {
            message = "Keep it up"
        }

        return message

}
pacing(currentDistance: 1, totalDistance: 10, currentTime: 6, goalTime: 60)

说明：首先，我使用 currentDistance 和 currentTime 来找到当前速度，然后我找到时间，或者你可以说如果我继续以当前速度继续完成总距离所需的估计时间，我这次从 calculatePace 函数返回，然后我将这个时间与目标时间进行了比较，如果我花更多的时间来完成总距离，那么我将不得不更加努力地推动，否则就只能跟上了。希望对你有帮助。

Answer 2

这是我使用更多步骤的方法，但对于像我这样的新手来说逻辑路径不太简洁：使用第一个函数打印估计完成时间（第一次作业要求）和 return 剩余时间（第二次作业要求），然后是第二个向跑步者发送消息的函数（也是第二个分配要求）：

func calculatePace(currentDistance:Double, totalDistance:Double, currentTime:Double) -> Double{
    let speed = currentDistance / currentTime
    let remainingDistance = totalDistance - currentDistance
    let remainingTime = remainingDistance / speed
    print("Estimated finish time: \(currentTime + remainingTime)")
    return remainingTime
}

func pacing(currentDistance:Double, totalDistance:Double, currentTime:Double, goalTime:Double){
    if (currentTime + calculatePace(currentDistance: currentDistance, totalDistance: totalDistance, currentTime: currentTime)) <= goalTime {
        print("Keep it up!")
    } else {
        print("You've got to push it just a bit harder!")
    }
}
pacing(currentDistance: 60, totalDistance: 240, currentTime: 15, goalTime: 60)

Answer 3

我就是这样做的。

func pacing(currentDistance: Double, totalDistance: Double, currentTime: Double, goalTime: Double) -> String {
if calculatePace(currentDistance: 17.9, totalDistance: 36, currentTime: 28.37) < goalTime {
    return "You've got to push it just a bit harder!"
} else {
    return "Keep it up!"
}

}

打印（起搏（当前距离：17.9，总距离：36，当前时间：28.37，目标时间：45））

如何解决 Apple 的 App Development With Swift iBook 中的第 2.2 课实验？

How to solve this lesson 2.2 lab in Apple's App Development With Swift iBook?

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