Question

我正忙着在Swiftty操场上使用SwiftyJSON解析JSON。我的代码如下：

import UIKit
import SwiftyJSON

var partyList: [String] = []
var firstPresidentList: [String] = []

if let url = URL(string:"http://mysafeinfo.com/api/data?list=presidents&format=json") {
    if let data = try? Data(contentsOf: url) {
        let json = JSON(data: data)
        for i in 1...43 {
            let party = json[i]["pp"].stringValue
            let president = json[i]["nm"].stringValue
            if partyList.contains(party) {
                print("\n")
            } else {
                partyList.append(party)
                firstPresidentList.append(president)
            }
        }
        print("All the different parties of U.S. presidents included "+partyList.joined(separator: ", ")+", in that order. The first presidents of those parties were (repectively) "+firstPresidentList.joined(separator: ", ")+".")
    }
}

在print行上，我想知道如何使用逗号和空格加入数组，就像我一样，但添加＆＃34;和＃34;在最后一个之前。

谢谢！

Answer 1

添加条件以检查您的String集合是否小于或等于2个元素，如果为true则返回" and "加入的两个元素，否则删除集合的最后一个元素，加入具有分隔符", "的元素然后使用最终分隔符", and "重新添加最后一个元素。

您可以将BidirectionalCollection协议的约束扩展到StringProtocol：

双向集合从任何有效集合向后提供遍历 index，不包括集合的startIndex。双向因此，集合可以提供其他操作，例如 last 属性，可以有效访问最后一个元素和a reverse（）方法以相反的顺序显示元素。

Swift 4.2或更高版本

extension BidirectionalCollection where Element: StringProtocol {
    var sentence: String {
        guard let last = last else { return "" }
        return count <= 2 ? joined(separator: " and ") :
            dropLast().joined(separator: ", ") + ", and " + last
    }
}


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

let sentenceFromElements = elements.sentence   // "a, b, and c"

Swift 4

extension BidirectionalCollection where Iterator.Element == String, SubSequence.Iterator.Element == String {
    var sentence: String {
        guard let last = last else { return "" }
        return count <= 2 ? joined(separator: " and ") :
            dropLast().joined(separator: ", ") + ", and " + last
    }
}

Swift 3.1或更高版本

extension Array where Element == String {
    var sentence: String {
        guard let last = last else { return "" }
        return count <= 2 ? joined(separator: " and ") :
            dropLast().joined(separator: ", ") + ", and " + last
    }
}

Answer 2

从iOS 13.0+ / macOS 10.15+开始，Apple提供了ListFormatter。另请参见here for details。

数组的格式可以很简单：

let elements = ["a", "b", "c"]
result = ListFormatter.localizedString(byJoining: elements)

正如函数名称所建议的那样，您还可以免费获得本地化。

用分隔符加入字符串数组＆＃34;，＆＃34;并添加＆＃34;和＆＃34;加入Swift中的最后一个元素

2 个答案: