SwiftUI: fileExporter does not appear

I develop iOS app and use fileExporter for exporting data to different text formats (csv, json etc). I moved "export" button view and models to separate files (struct and class) and got trouble when fileExporter does not appear. Seams like TextFileDocument is empty and I cant figure out why. Nothing happened after click on button "CSV". Thanks in advance for your ideas.

import SwiftUI
import UniformTypeIdentifiers

struct ExportButtonView: View {
    @ObservedObject private var vm: ExportButtonViewModel = ExportButtonViewModel()
    
    @State private var showingExporter: Bool = false
    @State private var showingChooseExportDataType: Bool = false
    
    var body: some View {
        Image(systemName: "square.and.arrow.up")
            .onTapGesture {
                showingChooseExportDataType.toggle()
            }
            .confirmationDialog("Choose data format to export", isPresented: $showingChooseExportDataType, titleVisibility: .visible) {
                Button("CSV") {
                    vm.initExportingTypeAndDocument(exportDataType: .csv)
                    showingExporter.toggle()
                }
                // Put here buttons for other formats
                .fileExporter(
                    isPresented: $showingExporter,
                    document: vm.exportingDocument,
                    contentType: .plainText,
                    defaultFilename: "data.\(vm.exportDataType)"
                ) { result in
                    switch result {
                    case .success(let url):
                        print("Saved to \(url)")
                    case .failure(let error):
                        print(error.localizedDescription)
                    }
                    
                }
            }
    }
}

class ExportButtonViewModel: ObservableObject {
    var exportDataType: TextFileDataExporterManager.ExportDataType = .csv
    var exportingDocument: TextFileDocument?
    
    func initExportingTypeAndDocument(exportDataType: TextFileDataExporterManager.ExportDataType){
        self.exportDataType = exportDataType
        self.exportingDocument = TextFileDocument(initialText: TextFileDataExporterManager(data: ["Test1", "Test2"], dataFormatType: exportDataType).getFormattedText())
    }
}

struct HomeView: View {
    var body: some View {
        ExportButtonView()
    }
}

protocol TextFileDataExporter {
    var data: [String] { get }
    func getFormattedText() -> String
}

class TextFileDataExporterManager: TextFileDataExporter {
    var data: [String]
    let dataFormatType: ExportDataType
    
    enum ExportDataType: String {
        case csv
    }
    
    init(data: [String], dataFormatType: ExportDataType) {
        self.data = data
        self.dataFormatType = dataFormatType
    }
    
    func getFormattedText() -> String {
        switch dataFormatType {
        case .csv:
            return CsvExporter(data: data).getFormattedText()
        }
    }
}

class CsvExporter: TextFileDataExporter {
    var data: [String]
    
    init(data: [String]) {
        self.data = data
    }
    
    func getFormattedText() -> String {
        return "Here;will;be;some;csv;data"
    }
}

struct TextFileDocument: FileDocument {
    // tell the system we support only plain text
    static var readableContentTypes = [UTType.plainText]

    // by default our document is empty
    var text = ""

    // a simple initializer that creates new, empty documents
    init(initialText: String = "") {
        text = initialText
    }

    // this initializer loads data that has been saved previously
    init(configuration: ReadConfiguration) throws {
        if let data = configuration.file.regularFileContents {
            text = String(decoding: data, as: UTF8.self)
        }
    }

    // this will be called when the system wants to write our data to disk
    func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper {
        let data = Data(text.utf8)
        return FileWrapper(regularFileWithContents: data)
    }
}