如何获取二维数组中某个项目的索引？

Question

如果我有一个数组：

let array = [
        ["Hamburger", "Nachos", "Lasagne"],
        ["Tomatoes", "Apples", "Oranges"],
        ["Soda", "Juice", "Water"]
    ]    

例如“Apples”的索引是什么？有没有办法以编程方式获取它？

Answer 1

您可以使用firstIndex(where:)并查找它的子索引firstIndex(of:)：

let array = [
    ["Hamburger", "Nachos", "Lasagne"],
    ["Tomatoes", "Apples", "Oranges"],
    ["Soda", "Juice", "Water"]
]

let query = "Apples"
if let index = array.firstIndex(where: {$0.contains(query)}),
    let subIndex = array[index].firstIndex(of: query) {
    print(array[index][subIndex])  // Apples

}

作为扩展：

extension Collection where Element: Collection, Element.Element: Equatable {
    func firstIndexAndSubIndex(of element: Element.Element) -> (index: Index, subIndex: Element.Index)? {
        if let index = firstIndex(where: {$0.contains(element)}),
            let subIndex = self[index].firstIndex(of: element) {
            return (index,subIndex)
        }
        return nil
    }
}

用法：

let array = [
    ["Hamburger", "Nachos", "Lasagne"],
    ["Tomatoes", "Apples", "Oranges"],
    ["Soda", "Juice", "Water"]
]
let query = "Soda"
if let indexes = array.firstIndexAndSubIndex(of: query) {
    print(indexes)   // "(index: 2, subIndex: 0)\n"
}

这也适用于从字符串数组中查找字符的索引：

let array = ["Hamburger", "Nachos", "Lasagne"]
let query: Character = "h"
if let indices = array.indexAndSubIndex(of: query) {
    print(indices)   // "(index: 1, subIndex: Swift.String.Index(_rawBits: 196865))\n"
    array[indices.index][indices.subIndex]  // "h"
}