swift - 计算耗时并更新所有任务

Question

我正在创建一个待办事项列表应用程序，它以秒为单位倒计时，直到下一个任务。

一旦完成一项任务，计时器就会开始倒计时，直到下一项任务，依此类推。

当应用程序打开时，这种情况会实时发生，但是当应用程序关闭时，计时器将停止，并且当前日期和时间存储在 NSUserDefaults 中，以便可以在打开时加载它们。

当应用程序打开时，我希望能够执行如下简单的操作:

let nextTaskIn   = 600.0 // example of were the last task was
let appClosed    = "2016-01-19 23:00:49 +0000" // example of time closed really comes from NSDate set on close
let timePassed   = NSDate().timeIntervalSinceDate(appClosed) // get num of seconds changed
let nextTaskTime = nextTaskIn - timePassed // example 600.0 - 120.0 = 480 seconds left

然后我可以将文本标签更新为 nextTaskTime 一切都很棒!

但是，当耗时比当前任务长并占用下一个任务时，就会出现问题。

例如:

let task1 = 90.0
let task2 = 180.0
let task3 = 270.0
let timePassed = 110.0
let nexTaskTime = task1 - timePassed // this is not correct

这是行不通的，它应该做的是使 task1 = 0. 和 task2 = 160.0 但递归地遍历所有或尽可能多的任务，直到已经没有了。

为了让它工作，我最好的想法是一个 while 循环，但我能想出的只是一个跟随，我已经没有想法了。

let task1 = 90.0
let task2 = 180.0
let task3 = 270.0
var timePassed = 110.0

while timePassed > 0 {
    let takenAway = timePassed - task1 // but unsure how to swap out for next task if task = 0
    timePassed = takenAway
} 

Answer 1

不确定这是否符合您的问题

let task1 = 90.0
let task2 = 180.0
let task3 = 270.0
var timePassed = 300.0
var tasks: [Double] = [task1, task2, task3] // init an array of your task

func updateTask(inout timePassed: Double) {
    for (index, _) in tasks.enumerate() { // enumerate your task
        let takenAway = timePassed - tasks[index]
        if takenAway <= 0 { // func should end here
            timePassed = 0
            tasks[index] = abs(takenAway)
            return
        }else { // keep going
            timePassed = takenAway
            tasks[index] = 0
        }
    }
}

updateTask(&timePassed)