Export Array using fileExporter - ios

Question

I am loading in a json file and creating an array. When a button is clicked, additional data is inserted into the array. What I want to do is export the modified array to a file. So essentially the array that has new data inserted into it.
What I'm not sure about is whether it is possible when exporting data from an array? or maybe I am going about this the wrong way?
EDIT: I don't necessarily want to export a json file, that was just the file type I first tried. I would be happy to export text files or csv's
ContentView
import SwiftUI
import UniformTypeIdentifiers
struct ContentView: View {
#State private var name = ""
#FocusState private var nameIsFocused: Bool
#State var labels: [LabelData] = []
#State var index = 0
#State var saveFile = false
var body: some View {
HStack {
Button(action: {
index += 1
if index <= labels.count {
labels[index - 1]._label = "Yellow" }
}) {
Text("Y")
}
Button(action: {
saveFile.toggle()
//print(labels[index - 1])
}) {
Text("Export")
.frame(width: 100, height: 100)
.foregroundColor(Color(red: 0.362, green: 0.564, blue: 1))
.background(Color(red: 0.849, green: 0.849, blue: 0.849))
.clipShape(RoundedRectangle(cornerRadius: 25.0, style: .continuous))
}
.offset(x: 0, y: 0)
.fileExporter(isPresented: $saveFile, document: Doc(url: Bundle.main.path(forResource: "labeldata", ofType: "json")!), contentType: .json) { (res) in
do {
let fileUrl = try res.get()
print(fileUrl)
}
catch {
print("cannot save doc")
print(error.localizedDescription)
}
}
}
VStack{
VStack {
if index < labels.count{
if let test = labels[index] {
Text(test._name)
}}}
.offset(x: 0, y: -250)
.frame(
minWidth: 0,
maxWidth: 325
)
VStack {
if index < labels.count{
if let test = labels[index] {
Text(test._name)
}}}
.offset(x: 0, y: -150)
.frame(
minWidth: 0,
maxWidth: 325
)
VStack {
if index < labels.count{
if let test = labels[index] {
Text(test._label)
}}}
.offset(x: 0, y: -50)
.frame(
minWidth: 0,
maxWidth: 325
)
}
.onAppear {
labels = load("labeldata.json")
}
}
}
struct Doc : FileDocument {
var url : String
static var readableContentTypes: [UTType]{[.json]}
init(url : String) {
self.url = url
}
init(configuration: ReadConfiguration) throws {
url = ""
}
func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper {
let file = try! FileWrapper(url: URL(fileURLWithPath: url), options: .immediate)
return file
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
LabelData
import Foundation
struct LabelData: Codable {
var _id: Int
var _name: String
var _type: String
var _description: String
var _label: String
}
labeldata.json
[
{
"_id" : 1,
"_name" : "Label1",
"_type" : "type1",
"_description" : "description1",
"_label" : ""
},
{
"_id" : 2,
"_name" : "Label2",
"_type" : "type2",
"_description" : "description2",
"_label" : ""
}
]
DataLoader
import Foundation
func load<T: Decodable>(_ filename: String) -> T {
let data: Data
guard let file = Bundle.main.url(forResource: filename, withExtension: nil)
else {
fatalError("Couldn't find \(filename) in main bundle.")
}
do {
data = try Data(contentsOf: file)
} catch {
fatalError("Couldn't load \(filename) from main bundle:\n\(error)")
}
do {
let decoder = JSONDecoder()
return try decoder.decode(T.self, from: data)
} catch {
fatalError("Couldn't parse \(filename) as \(T.self):\n\(error)")
}
}

Answer 1

The fileExporter writes in-memory data to location selected by a user, so we need to create document with our content and generate FileWrapper from content to exported data (CSV in this example).
So main parts, at first, exporter:
.fileExporter(isPresented: $saveFile,
document: Doc(content: labels), // << document from content !!
contentType: .plainText) {
and at second, document:
struct Doc: FileDocument {
static var readableContentTypes: [UTType] { [.plainText] }
private var content: [LabelData]
init(content: [LabelData]) {
self.content = content
}
// ...
// simple wrapper, w/o WriteConfiguration multi types or
// existing file selected handling (it is up to you)
func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper {
let text = content.reduce("") {
$0 + "\($1._id),\($1._name),\($1._type),\($1._description),\($1._label)\n"
}
return FileWrapper(regularFileWithContents:
text.data(using: .utf8) ?? Data()) // << here !!
}
Tested with Xcode 13.4 / iOS 15.5
Test module is here

Answer 2

It sounds like you want to create a new JSON file from the modified data within the array. It is a bit unusual to want to create a new JSON file. Maybe you want to persist the data? In that case you wouldn't save it as JSON you would persist it with a proper DB (DataBase) like CoreData, FireBase, Realm, or ect...
But if you really want to do this. Then you need to create a new JSON file from the data in the array. You have a load<T: Decodable> function but you are going to want a save<T: Codable> function. Most people would, once again, use this opportunity to save the data to a DB.
This guys does a pretty good job explaining this: Save json to CoreData as String and use the String to create array of objects
So here is a good example of saving JSON data to a file:
let jsonString = "{\"location\": \"the moon\"}"
if let documentDirectory = FileManager.default.urls(for: .documentDirectory,
in: .userDomainMask).first {
let pathWithFilename = documentDirectory.appendingPathComponent("myJsonString.json")
do {
try jsonString.write(to: pathWithFilename,
atomically: true,
encoding: .utf8)
} catch {
// Handle error
}
}