let x where x.hasSuffix("pepper") 如何工作 [英] How does let x where x.hasSuffix("pepper") work

问题描述

在下面的代码块中，我无法理解 let x where x.hasSuffix("pepper").

let菜=红辣椒"切换蔬菜{案例芹菜":letvegetableComment = "添加一些葡萄干并在原木上制作蚂蚁."案例黄瓜"，豆瓣菜":让蔬菜评论 = "那会是一个很好的茶三明治"case let x where x.hasSuffix("pepper"):让蔬菜评论 = "辣吗\(x)"默认:让蔬菜评论 = "汤里的一切都很好吃."}

<块引用>

控制台输出

vegetableComment:是辣红辣椒吗

似乎发生了以下逻辑.

x = 蔬菜if (x 的后缀 == 'pepper')运行案例

有人可以为我更好地解释一下吗?

解决方案

vegetable 是一个隐式的 String.和你写的一样:

var 蔬菜:String = "红辣椒"

hasSuffix 声明为 func hasSuffix(suffix: String) ->Bool 因此返回一个 Bool.where 关键字指定了附加要求，并且只能在 switch 语句中使用.
因为这一切都被泛滥了，vegetable 变量被赋值给了 x (let x).

您可以阅读有关 where 和 switch 的更多信息 此处.

In the code block below, I am having trouble understanding let x where x.hasSuffix("pepper").

let vegetable = "red pepper"

switch vegetable {
    case "celery":
        let vegetableComment = "Add some raisins and make ants on a log."
    case "cucumber", "watercress":
        let vegetableComment = "That would make a good tea sandwhich"
    case let x where x.hasSuffix("pepper"):
        let vegetableComment = "Is it a spicy \(x)"
    default:
        let vegetableComment = "Everything tastes good in soup."
}

Console output

vegetableComment: Is it a spicy red pepper

It seems like the following logic is happening.

x = vegetable
if (x's suffix == 'pepper') 
    run case

Can someone explain this better for me?

解决方案

vegetable is an implicit String. It's the same as you would write:

var vegetable: String = "red pepper"

hasSuffix is declared as func hasSuffix(suffix: String) -> Bool an therefore returns a Bool. The where keyword specifies additional requirements, and can only be used in switch statements.
Because all of this is suffused, the vegetable variable is assigned to x (let x).

You can read more about the where and switch here.

这篇关于let x where x.hasSuffix("pepper") 如何工作的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！