如何计算账单总额？

Question

我正在尝试计算账单上的总金额，但看不到如何去做。这是我正在学习的教程中写的，因为我正在学习SwiftUI。

有关如何操作的任何提示？

username    sum_all_games_points
John        32                -- This is the sum of (10 + 8 + 7 + 3 + 4)
Martha      2                 -- Only one game played on game2
Adam        10                -- 9 points from game1 and 1 point from game2

这是我正在做的一个教程，这是您可以做的额外挑战。我认为做额外的挑战会很好，我尝试了不同的方法，但只在SwiftUI中收到错误消息。

Answer 1

一种方法是重构totalPerPerson的计算方式。如果您查看一下计算，实际上是在计算账单的总数。

var totalPerPerson: Double {
    let peopleCount = Double(numberOfPeople + 2)
    let tipSelection = Double(tipPercentages[tipPercentage])
    let orderAmount = Double(checkAmount) ?? 0

    let tipValue = orderAmount / 100 * tipSelection
    let grandTotal = orderAmount + tipValue        // <- this is the total amount of the bill
    let amountPerPerson = grandTotal / peopleCount

    return amountPerPerson
}

---

如果您创建一个名为grandTotal的附加变量，则可以重构totalPerPerson变量以使用此新变量。

// this is the code used in the totalPerPerson to calculate the grandTotal
var grandTotal: Double {
    let tipSelection = Double(tipPercentages[tipPercentage])
    let orderAmount = Double(checkAmount) ?? 0

    let tipValue = orderAmount / 100 * tipSelection
    let grandTotal = orderAmount + tipValue
    return grandTotal
}

// The totalPerPerson uses the above grandTotal variable to calculate its value
var totalPerPerson: Double {
    let peopleCount = Double(numberOfPeople + 2)
    let amountPerPerson = grandTotal / peopleCount
    return amountPerPerson
}

然后由您决定如何在屏幕上显示它。