Copy CoreData data to CSV file - swiftui

Question

I am trying to use fileExport logic to copy history data from CoreData to a CSV file. Since the data is coming from CoreData I need to use #FetchRequest and it is my understanding that #FetchRequest may only be used in a view.
I'm getting a number of errors related to misusing a view and transferring the data to fileExporter. It seems like I'm misusing a view to transfer data. Are there other features of CoreData that can be used to retrieve data outside of a view?
I have several similar structures that create CSV files without using coreData working. Therefore I believe my structures CreateHistoryTable and MessageDocument are working correctly. So I need help getting my data from CoreData to fileExporter.
struct CreateHistoryTable: View {
#Environment(\.managedObjectContext) var viewContext
#State private var showingExporter: Bool = false
#State private var document: MessageDocument?
var body: some View {
VStack {
Button ( action: {
self.showingExporter = true
document = CreateHistoryCSV() <-- need help here retrieving document to export
}) {
HStack (alignment: .firstTextBaseline) {
Text("Export History Entries")
.fontWeight(.bold)
.font(.title3)
Image(systemName: "square.and.arrow.up")
}
}
}.fileExporter(
isPresented: $showingExporter,
document: document,
contentType: .plainText,
defaultFilename: "TripSenseHistory.csv"
) { result in
switch result {
case .success(let url):
print("Saved to \(url)")
case .failure(let error):
print(error.localizedDescription)
}
}
.navigationBarTitle(Text("Export History Entries"), displayMode: .inline)
}
}
Retrieve data from CoreData and copy to single text string
struct CreateHistoryCSV: View {
#Binding MessageDocument
var csvData: String = ""
var title = ",Trip Sense History Entries,\n"
var subtitle = "Date,Category,Payment Type, Amount\n"
var messageRow: String = ""
var sHisCatName: String = ""
var sHisDsc: String = ""
var sHisPayType: String = ""
var sHisMoney: String = ""
var dHisMoney: Double = 0.0
var sHisLoc: String = ""
var payType = ["Cash", "Debit", "Credit"]
var code: String = ""
var messageRow = ""
// fetch core data
#FetchRequest(
entity: CurrTrans.entity(),
sortDescriptors: [NSSortDescriptor(keyPath: \CurrTrans.entryDT, ascending: true)]
) var currTrans: FetchedResults<CurrTrans>
var body: some View {
var csvData = title + subtitle
for item in 0..<currTrans.count {
let messageRow = createHistoryRow(item: item)
csvData += messageRow
}
print(csvData)
//return MessageDocument(message: csvData)
}
func createHistoryRow(item: Int) ->(String) {
// format expense date and time
let dHisDate = currTrans[item].entryDT ?? Date()
let sHisDate = dHisDate.formatted(.dateTime.year().day().month(.wide).hour().minute())
// get history category
let sHisCatName = currTrans[item].entryCatName ?? "cat name"
// get payment type
let sHisPayType = payType[Int(currTrans[item].entryPT)]
// get description
let sHisDsc = currTrans[item].entryDsc ?? "Unk"
// format transaction amount
let code = currTrans[item].entryCode ?? "Unk" // 3 digit country code for this transaction
let dHisMoney = currTrans[item].entryMoney
let sHisMoney = dHisMoney.formatted(.currency(code: sym))
// get location
let sHisLoc = currTrans[item].entryAddr ?? "Unk"
messageRow = "\"\(sHisDate)\"" + "," + sHisCatName + "," + sHisPayType + "," + "\"\(sHisDsc)\"" + "," + "\"\(sHisMoney)\"" + "," + "\"\(sHisLoc)\"" + "\n"
return messageRow
}
}
This code is part of the Swiftui file export logic
struct MessageDocument: FileDocument {
static var readableContentTypes: [UTType] { [.plainText] }
var message: String = ""
init(message: String) {
self.message = message
}
init(configuration: ReadConfiguration) throws {
guard let data = configuration.file.regularFileContents,
let string = String(data: data, encoding: .utf8)
else {
throw CocoaError(.fileReadCorruptFile)
}
message = string
}
// this will be called when the system wants to write our data to disk
func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper {
return FileWrapper(regularFileWithContents: message.data(using: .utf8)!)
}
}

Answer 1

With further research I realized that I could place the #FetchRequest in CreateHistoryTable along with the fileExporter view logic. That allowed me to change CreateHistoryCSV to a function of CreateHistoryTable. No changes were made to createHistoryRow
// copy history entrys to csv file
struct CreateHistoryTable: View {
#EnvironmentObject var base: BaseCurrency
#EnvironmentObject var bank: BankWithdrawal
#EnvironmentObject var userData: UserData
#Environment(\.managedObjectContext) var viewContext
#State private var showingExporter: Bool = false
#State private var document: MessageDocument?
var title = ",Trip Sense History Entries,\n"
var subtitle = "Date,Category,Payment Type, Amount\n"
var messageRow: String = ""
var sHisCatName: String = ""
var sHisDsc: String = ""
var sHisPayType: String = ""
var sHisMoney: String = ""
var dHisMoney: Double = 0.0
var sHisLoc: String = ""
var payType = ["Cash", "Debit", "Credit"]
var sym: String = ""
// fetch core data
#FetchRequest(
entity: CurrTrans.entity(),
sortDescriptors: [NSSortDescriptor(keyPath: \CurrTrans.entryDT, ascending: true)]
) var currTrans: FetchedResults<CurrTrans>
var body: some View {
VStack {
Button ( action: {
self.showingExporter = true
let dates = userData.formatCsvDate(startDate: startDate, endDate: endDate)
document = CreateHistoryCSV(dates: dates)
}) {
HStack (alignment: .firstTextBaseline) {
Text("Export History Entries")
.fontWeight(.bold)
.font(.title3)
Image(systemName: "square.and.arrow.up")
}
}
}.fileExporter(
isPresented: $showingExporter,
document: document,
contentType: .plainText,
defaultFilename: "TripSenseHistory.csv"
) { result in
switch result {
case .success(let url):
print("Saved to \(url)")
case .failure(let error):
print(error.localizedDescription)
}
}
.navigationBarTitle(Text("Export History Entries"), displayMode: .inline)
}
func CreateHistoryCSV() -> (MessageDocument) {
var csvData = title + subtitle
for item in 0..<currTrans.count {
let messageRow = createHistoryRow(item: item)
csvData += messageRow
}
print(csvData)
return MessageDocument(message: csvData)
}