在SwiftUI中动态创建list的section

Question

我正在尝试动态地为List创建一个标题在SwiftUI节。

这是我的数组:

var lists = [a list of names with A to Z] // array of strings

然后我试着得到第一个字母:

var firstCharacters: [Character] {
var firstCharacters = [Character]()
for list in lists.sorted(by: {$0 < $1}) {
if let character = list.first, !firstCharacters.contains(character) {
firstCharacters.append(character)
}
}
return firstCharacters
}

我这样创建了list:

List {
ForEach(firstCharacters, id: .self) { charachter in
Section(header: Text("(charachter.description)")) {
ForEach(Array(lists.enumerated()), id:.element) {  index, element in
Text("Name (element), Id: (index)")
})
}
}
}
}

现在我在向列表添加section时遇到了问题，现在我不知道如何与列表结合。

Answer 1

更好的划分方法是将单词列表转换成按首字母键的字典，如下所示:

var wordDict: [String:[String]] {
let letters = Set(lists.compactMap( { $0.first } ))
var dict: [String:[String]] = [:]
for letter in letters {
dict[String(letter)] = lists.filter( { $0.first == letter } ).sorted()
}
return dict
}

然后像这样在你的List中使用Dict:

List {
// You then make an array of keys, sorted by lowest to highest
ForEach(Array(wordDict.keys).sorted(by: <), id: .self) { character in
Section(header: Text("(character)")) {
// Because a dictionary lookup can return nil, we need to provide a response
// if it fails. I used [""], though I could have just force unwrapped.
ForEach(wordDict[character] ?? [""], id: .self) { word in
Text("Name (word)")
}
}
}
}

这使您不必为每个字母遍历整个列表。在创建Dict时只执行一次。你不再需要var firstChar.

Answer 2

下面将打印每个部分中的名称:

struct ContactsView: View {
let names = ["James", "Steve", "Anna", "Baxter", "Greg", "Zendy", "Astro", "Jenny"]
var firstChar: [Character] {
let array =  names
.compactMap({ $0.first })

// Set is just a quick way to remove duplicates.
return Array(Set(array))
.sorted(by: { $0 < $1 })
}
var body: some View {
List {
ForEach(firstChar, id: .self) { char in
Section(header: Text("(char.description)")) {
ForEach(names, id: .self) { name in
if name.first == char {
Text(name)
}
}
}
}
}
}
}

尽管更好的方法可能是不要有两个不同的数组，而是将它们合并成一个数组，其中第一个字母是键，值是名称。

这样就不必遍历每个section的每个名称了。

Answer 3

我的建议是一个视图模型，它将字符串数组与Dictionary(grouping:by:)组成Section结构体

class ViewModel : ObservableObject {
struct Section: Identifiable {
let letter : String
let names : [String]

var id : String { letter }
}

@Published var sections = [Section]()

var names = [String]() {
didSet {
let grouped = Dictionary(grouping: names, by: {$0.prefix(1)})
sections = grouped.keys.sorted().map{Section(letter: String($0), names: grouped[$0]!)}
}
}
}

每当数组的内容被修改时，section数组(和视图)都会被更新。

---

在onAppear的视图中pass一些名称

struct ContentView: View {
@StateObject private var model = ViewModel()
var body: some View {

List(model.sections) { section in
Section(section.letter) {
ForEach(section.names, id: .self, content: Text.init)
}
}
.onAppear {
model.names = ["Aaran", "Aaren", "Aarez", "Badsha", "Bailee", "Bailey", "Bailie", "Bailley", "Carlos", "Carrich", "Carrick", "Carson", "Carter", "Carwyn", "Dante", "Danyal", "Danyil", "Danys", "Daood", "Dara", "Darach", "Daragh", "Darcy", "D'arcy", "Dareh", "Eisa", "Eli", "Elias", "Elijah", "Eliot", "Elisau", "Finn", "Finnan", "Finnean", "Finnen", "Finnlay", "Geoff", "Geoffrey", "Geomer", "Geordan", "Hamad", "Hamid", "Hamish", "Hamza", "Hamzah", "Han", "Idris", "Iestyn", "Ieuan", "Igor", "Ihtisham", "Jarno", "Jarred", "Jarvi", "Jasey-Jay", "Jasim", "Jaskaran", "Jason", "Jasper", "Jaxon", "Kabeer", "Kabir", "Kacey", "Kacper", "Kade", "Kaden", "Kadin", "Kadyn", "Kaeden", "Kael", "Kaelan", "Kaelin", "Kaelum", "Kai", "Kaid", "Kaidan", "Kaiden", "Kaidinn", "Kaidyn", "Kaileb", "Kailin", "Karsyn", "Karthikeya", "Kasey", "Kash", "Kashif", "Kasim", "Kasper", "Kasra", "Kavin", "Kayam", "Leiten", "Leithen", "Leland", "Lenin", "Lennan", "Lennen", "Lennex", "Lennon", "Lennox", "Lenny", "Leno", "Lenon", "Lenyn", "Leo", "Leon", "Leonard", "Leonardas", "Leonardo", "Lepeng", "Leroy", "Leven", "Levi", "Levon", "Machlan", "Maciej", "Mack", "Mackenzie", "Mackenzy", "Mackie", "Macsen", "Macy", "Madaki", "Nickson", "Nicky", "Nico", "Nicodemus", "Nicol", "Nicolae", "Nicolas", "Nidhish", "Nihaal", "Nihal", "Nikash", "Olaoluwapolorimi", "Ole", "Olie", "Oliver", "Olivier", "Peter", "Phani", "Philip", "Philippos", "Phinehas", "Phoenix", "Phoevos", "Pierce", "Pierre-Antoine", "Pieter", "Pietro", "Piotr", "Porter", "Prabhjoit", "Prabodhan", "Praise", "Pranav", "Rasul", "Raul", "Raunaq", "Ravin", "Ray", "Rayaan", "Rayan", "Rayane", "Rayden", "Rayhan", "Santiago", "Santino", "Satveer", "Saul", "Saunders", "Savin", "Sayad", "Sayeed", "Sayf", "Scot", "Scott", "Scott-Alexander", "Seaan", "Seamas", "Seamus", "Sean", "Seane", "Sean-James", "Sean-Paul", "Sean-Ray", "Seb", "Sebastian", "Sebastien", "Selasi", "Seonaidh", "Sephiroth", "Sergei", "Sergio", "Seth", "Sethu", "Seumas", "Shaarvin", "Shadow", "Shae", "Shahmir", "Shai", "Shane", "Shannon", "Sharland", "Sharoz", "Shaughn", "Shaun", "Tadhg", "Taegan", "Taegen", "Tai", "Tait", "Uilleam", "Umair", "Umar", "Umer", "Umut", "Urban", "Uri", "Usman", "Uzair", "Uzayr", "Valen", "Valentin", "Valentino", "Valery", "Valo", "Vasyl", "Vedantsinh", "Veeran", "Victor", "Victory", "Vinay", "Vince", "Wen", "Wesley", "Wesley-Scott", "Wiktor", "Wilkie", "Will", "William", "William-John", "Willum", "Wilson", "Windsor", "Wojciech", "Woyenbrakemi", "Wyatt", "Wylie", "Wynn", "Xabier", "Xander", "Xavier", "Xiao", "Xida", "Xin", "Xue", "Yadgor", "Yago", "Yahya", "Yakup", "Yang", "Yanick", "Yann", "Yannick", "Yaseen", "Yasin", "Yasir", "Yassin", "Yoji", "Yong", "Yoolgeun", "Yorgos", "Youcef", "Yousif", "Youssef", "Yu", "Yuanyu", "Yuri", "Yusef", "Yusuf", "Yves", "Zaaine", "Zaak", "Zac", "Zach", "Zachariah", "Zacharias", "Ziyaan", "Zohaib", "Zohair", "Zoubaeir", "Zubair", "Zubayr", "Zuriel"]
}
}
}