How to filter by ALL if input is empty? SwiftUI/Core Data

Below in my code I have simple setup whereby my FetchRequest is filtered by a string, this string comes from a text field that the user can input into. How do I return all results if said text field is empty?

struct TechList: View {

var fetchRequest: FetchRequest<HearingDevice>
@State private var selectedDevice: String?
@ObservedObject var model = Model()
init(filter: String) {
    fetchRequest = FetchRequest<HearingDevice>(entity: HearingDevice.entity(), sortDescriptors: [], predicate: NSPredicate(format: "model CONTAINS %@", filter))

}

var body: some View {
    VStack(alignment: .center){
        List(fetchRequest.wrappedValue, id: \.self) { device in
            VStack(alignment: .center) {
                HStack{
                    Text(device.model ?? "Unknown" + " ")
                        .font(.system(size: 17))
                        .fontWeight(.medium)
                     .foregroundColor(self.selectedDevice == device.model ? Color.white:Color.init(hex: "47535B"))
                         .multilineTextAlignment(.leading)
                        .padding(.leading)
                 Spacer()
             }
            }
            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: 60)
            .background(self.selectedDevice == device.model ? Color.init(hex: "666699"):Color.init(hex: "F6F6F6"))
            .cornerRadius(7.0)
            .onTapGesture {
            self.model.deviceModel = device.model!
             withAnimation(.spring()){
                 self.selectedDevice = device.model!
             }
          }
        }
        .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: .infinity)
        .padding(.top, 160.0)
        .padding(.bottom, 20.0)
    }
  }
}

Is there a way I can return ALL of my results if there is no filter provided?

Update based on Asperi's comment:

struct TechList: View {
var filter: String
@FetchRequest(fetchRequest: HearingDevice.fetchRequest()) var fetchRequest: FetchedResults<HearingDevice>
@State private var selectedDevice: String?
@ObservedObject var model = Model()
init(filter: String) {
    self.filter = filter
    _fetchRequest = FetchRequest<HearingDevice>(entity: HearingDevice.entity(), sortDescriptors: [], predicate: NSPredicate(format: "model CONTAINS %@", filter))

}

var body: some View {
    VStack(alignment: .center){
        List(fetchRequest, id: \.self) { device in
            VStack(alignment: .center) {
                HStack{
                    Text(device.model ?? "Unknown" + " ")
                        .font(.system(size: 17))
                        .fontWeight(.medium)
                     .foregroundColor(self.selectedDevice == device.model ? Color.white:Color.init(hex: "47535B"))
                         .multilineTextAlignment(.leading)
                        .padding(.leading)
                 Spacer()
             }
            }
            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: 60)
            .background(self.selectedDevice == device.model ? Color.init(hex: "666699"):Color.init(hex: "F6F6F6"))
            .cornerRadius(7.0)
            .onTapGesture {
            self.model.deviceModel = device.model!
             withAnimation(.spring()){
                 self.selectedDevice = device.model!
             }
          }
        }
        .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: .infinity)
        .padding(.top, 160.0)
        .padding(.bottom, 20.0)
     }
   }
 }

I have implemented the approach from your first comment although there are no errors and the code executes fine, my list remains empty. How do I pull the fetch request into my list if I am not using .wrappedValue?