尽管不再满足循环条件，但仍卡在 While 循环中答案

【问题标题】：Stuck in While loop despite condition for loop no longer being met尽管不再满足循环条件，但仍卡在 While 循环中
【发布时间】：2020-05-18 22:37:50
【问题描述】：

我对 Swift 编码非常陌生，现在我正在尝试编写一个程序，它只需要预算和一些餐馆，然后尝试根据剩余的预算量来确定你要吃什么。似乎我的代码应该可以工作，但是由于某种原因，当它在一定次数的迭代后进入 while 循环时，它无法识别何时 totalPrice 不再大于预算。如果我在 while 循环的末尾放置一个 if 条件，验证 totalPrice 是否大于预算，它将识别它不是，然后执行我放在花括号中的任何内容，但不会离开 while 循环。我真的对出了什么问题感到困惑，并且非常感谢一些帮助理解我的代码出了什么问题。非常感谢您的帮助！

import UIKit

var prices = [30,10.99,10.5,11.7,13.99,7.99,8.99,0]
var tips = [0.20,0.18,0.18,0.18,0.18,0.15,0.15,0.0]
var restaurants = ["Salty Snow","Kerby Lane","Milto's","Trudy's","Madam Mam's","Vert's","Teji's","Home"]
var daysOfWeek = ["Sunday", "Monday", "Tuesday","Wednesday", "Thursday", "Friday", "Saturday"]
let taxRate = 0.0825
var budget = 50.0

for i in 1...14{
    print("Week \(i)")
    for day in daysOfWeek {
        var randInt = Int.random(in:0..<8)
        var totalPrice = prices[randInt]+(prices[randInt]*taxRate)+(prices[randInt]*tips[randInt])
        while totalPrice > budget {
            var randInt = Int.random(in:0..<8)
            var totalPrice = prices[randInt]+(prices[randInt]*taxRate)+(prices[randInt]*tips[randInt])
        }
        print(totalPrice, randInt, budget)
        var place = restaurants[randInt]
        budget = budget - totalPrice
        print("\(day) meal: \(place), budget now \(budget)")

    }
    print()
    budget += 50
}

【问题讨论】：

你想实现什么兄弟？从那么多循环中
您在 while 循环中创建了一个新的 totalPrice 变量，因此它与您在 while 循环的条件中使用的不同。在while 循环内将var totalPrice = ... 更改为totalPrice = ...。对于这种情况，使用调试器将是一件好事。投票结束这是一个错字。
是的，我是个白痴，非常感谢
嗯，我们都会不时犯一些简单的错误，就像我说的那样，调试器是发现这些错误的好工具。顺便说一句，你对randInt 做同样的事情，是故意的吗？

标签： ios swift while-loop infinite-loop

【解决方案1】：

当您在 while 循环中添加 var totalPrice 而不是更新 totalPrice 时，您定义了一个具有相同名称的新变量，这就是为什么条件永远不会匹配并变成无限循环的原因。使用这个：

var prices = [30,10.99,10.5,11.7,13.99,7.99,8.99,0]
var tips = [0.20,0.18,0.18,0.18,0.18,0.15,0.15,0.0]
var restaurants = ["Salty Snow","Kerby Lane","Milto's","Trudy's","Madam Mam's","Vert's","Teji's","Home"]
var daysOfWeek = ["Sunday", "Monday", "Tuesday","Wednesday", "Thursday", "Friday", "Saturday"]
let taxRate = 0.0825
var budget = 50.0

for i in 1...14{
print("Week \(i)")
for day in daysOfWeek {
    let randInt = Int.random(in:0..<8)
    var totalPrice = prices[randInt]+(prices[randInt]*taxRate)+(prices[randInt]*tips[randInt])
    while totalPrice > budget {
        let randInt = Int.random(in:0..<8)
        totalPrice = prices[randInt]+(prices[randInt]*taxRate)+(prices[randInt]*tips[randInt])
        print(totalPrice, randInt, budget)

    }
    let place = restaurants[randInt]
    budget = budget - totalPrice
    print("\(day) meal: \(place), budget now \(budget)")

}
print()
budget += 50
}

【讨论】：

【解决方案2】：

从 while 循环中的 totalPrice 变量中删除 var... 因为它不会改变而是每次都创建新变量

 while totalPrice > budget {
    var randInt = Int.random(in:0..<8)
        totalPrice = prices[randInt]+(prices[randInt]*taxRate)+(prices[randInt]*tips[randInt])
  //var totalPrice = prices[randInt]+(prices[randInt]*taxRate)+(prices[randInt]*tips[randInt])
     }

【讨论】：