How to Append to Array of Structs and have Change Persistant? - swiftui

Question

I want to be able to store a list of objects in a separate Swift file and call them in a page to have them show up. I successful did this with this code:
import Foundation
import SwiftUI
struct MatchInfo: Hashable, Codable {
let theType: String
let theWinner: String
let theTime: String
let id = UUID()
}
var matchInfo = [
MatchInfo(theType: "Capitalism", theWinner: "Julia", theTime: "3/3/2021"),
MatchInfo(theType: "Socialism", theWinner: "Julia", theTime: "3/2/2021"),
MatchInfo(theType: "Authoritarianism", theWinner: "Luke", theTime: "3/1/2021")
]
where I append to the list after a match is played on another page here:
matchInfo.insert(MatchInfo(theType: typeSelection, theWinner: winnerName, theTime: "\(datetimeWithoutYear)" + "\(year)"), at: 0)
And heres some of the code on another page where I call it into a list:
List {
ForEach(matchInfo, id: \.self) { matchData in
matchRow(matchData : matchData)
} .background(Color("invisble"))
.listRowBackground(Color("invisble"))
} .frame(height: 490)
...
struct matchRow: View {
let matchData: MatchInfo
var body: some View {
HStack {
VStack(alignment: .leading) {
Text(matchData.theType)
.font(.system(size: 20, weight: .medium, design: .default))
Text(" Winner: " + matchData.theWinner)
}
Spacer()
Text(matchData.theTime)
.padding(.leading, 40)
.multilineTextAlignment(.trailing)
}
.foregroundColor(.white)
.accentColor(.white)
}
}
But this code doesn't save through app restarts. I've never had something save through a restart before and have been struggling to find an answer simple enough for me to understand. How can I update the list without it going away next time I open the app?

Answer 1

Okay so here is an example on how you save to/ load from the documents folder.
First of all make sure that you object MatchInfo conforms to this protocol.
import Foundation
protocol LocalFileStorable: Codable {
static var fileName: String { get }
}
extension LocalFileStorable {
static var localStorageURL: URL {
guard let documentDirectory = FileManager().urls(for: .documentDirectory, in: .userDomainMask).first else {
fatalError("Can NOT access file in Documents.")
}
return documentDirectory
.appendingPathComponent(self.fileName)
.appendingPathExtension("json")
}
}
extension LocalFileStorable {
static func loadFromFile() -> [Self] {
do {
let fileWrapper = try FileWrapper(url: Self.localStorageURL, options: .immediate)
guard let data = fileWrapper.regularFileContents else {
throw NSError()
}
return try JSONDecoder().decode([Self].self, from: data)
} catch _ {
print("Could not load \(Self.self) the model uses an empty collection (NO DATA).")
return []
}
}
}
extension LocalFileStorable {
static func saveToFile(_ collection: [Self]) {
do {
let data = try JSONEncoder().encode(collection)
let jsonFileWrapper = FileWrapper(regularFileWithContents: data)
try jsonFileWrapper.write(to: self.localStorageURL, options: .atomic, originalContentsURL: nil)
} catch _ {
print("Could not save \(Self.self)s to file named: \(self.localStorageURL.description)")
}
}
}
extension Array where Element: LocalFileStorable {
///Saves an array of LocalFileStorables to a file in Documents
func saveToFile() {
Element.saveToFile(self)
}
}
Your main Content View should look like this: (I modified your object to make it a bit simpler.)
import SwiftUI
struct MatchInfo: Hashable, Codable, LocalFileStorable {
static var fileName: String {
return "MatchInfo"
}
let description: String
}
struct ContentView: View {
#State var matchInfos = [MatchInfo]()
var body: some View {
VStack {
Button("Add Match Info:") {
matchInfos.append(MatchInfo(description: "Nr." + matchInfos.count.description))
MatchInfo.saveToFile(matchInfos)
}
List(matchInfos, id: \.self) {
Text($0.description)
}
.onAppear(perform: {
matchInfos = MatchInfo.loadFromFile()
})
}
}
}