我是一个菜鸟，试图用苹果的"App Development With Swift"iBook学习swift，似乎无法完成2.2课函数的最后实验。谁能指导我正确完成实验？ 以下是实验室的要求：现在编写一个名为 paceing 的函数，该函数采用四个双精度参数，分别称为 currentDistance、totalDistance、currentTime 和 goalTime。该函数还应返回一个字符串，该字符串将是向用户显示的消息。该函数应调用 calculatePace，传入适当的值，并捕获返回值。然后，该函数应将返回的值与 goalTime 进行比较，如果用户在配速，则返回"坚持下去！"，否则返回"你必须用力一点！调用该函数并打印返回值。
以下是我之前在实验室不同部分的计算速度函数：
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的功能，但遇到了麻烦：
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返回值，实验室的最后几句话让我感到困惑。"如果用户在跟上步伐返回"坚持下去！"，然后返回"你必须用力一点！"否则。调用该函数并打印返回值。这不是两个不同的打印件吗，那么我如何返回两者，否则部分是什么意思？
我觉得这就是你想要的，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)
解释： 首先我用currentDistance和currentTime找到当前速度，然后我找到时间或者你可以说如果我继续保持当前速度，我会花费的时间来完成总距离，我从calculatePace函数返回这个时间，然后我把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，否则就跟上。希望对您有所帮助。
这是我使用更多步骤的方法，而对于像我这样的菜鸟来说，逻辑路径不那么简洁： 使用第一个函数打印估计完成时间(第一个分配要求(并返回剩余时间(第二个分配要求(，然后第二个函数向运行器发送消息(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)
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(步调(当前距离： 17.9， 总距离： 36， 当前时间： 28.37， 目标时间： 45((