如何在 Swift 中查找列表项的索引?

问题描述

我正在尝试通过搜索 list 来查找 item index.有人知道该怎么做吗?

I am trying to find an item index by searching a list. Does anybody know how to do that?

我看到有 list.StartIndex 和 list.EndIndex 但我想要类似 python 的 list.index("text") 的东西.

I see there is list.StartIndex and list.EndIndex but I want something like python's list.index("text").

推荐答案

由于 swift 在某些方面比面向对象更具功能性(并且数组是结构，而不是对象)，所以使用函数find"；对数组进行操作，它返回一个可选值，所以准备处理一个 nil 值:

As swift is in some regards more functional than object-oriented (and Arrays are structs, not objects), use the function "find" to operate on the array, which returns an optional value, so be prepared to handle a nil value:

let arr:Array = ["a","b","c"]
find(arr, "c")!              // 2
find(arr, "d")               // nil

使用 firstIndex 和 lastIndex - 取决于您要查找项目的第一个索引还是最后一个索引:

Use firstIndex and lastIndex - depending on whether you are looking for the first or last index of the item:

let arr = ["a","b","c","a"]

let indexOfA = arr.firstIndex(of: "a") // 0
let indexOfB = arr.lastIndex(of: "a") // 3

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