SwiftUI Picker in a TextField with Core Data, error “Result of 'Picker <Label, SelectionValue, Content>' initializer is unused”

An app of filing that has a form with a Picker and two entities behind, one-many relationship. Want to save a Picker value picked from one entity and save into the other, specifically a value picked from cateName.CatesEnt saved into fileName.FilesEnt via a TextField. Tried with the code below but got a yellow stopper error.

struct FileAddEdit: View {

@ObservedObject var fileData : FileVM
@Environment(\.managedObjectContext) var context
@FetchRequest(sortDescriptors: [NSSortDescriptor(keyPath: \CatesEnt.cateOrder, ascending: true)], animation: .default)
private var cates: FetchedResults<CatesEnt>
@State var selectedCate: CatesEnt? = nil
@State var cateName: [CatesEnt] 

...
HStack {
  Text("File Name:")
  TextField("required", text: $fileData.fileName)
}
HStack {
    Text("Folder:")
    TextField("select a folder", text: $fileData.fileCate)
    .onTapGesture {
        Picker(selection: $selectedCate, label: Text("folder: ")) {
        // yellow stopper waning: "Result of 'Picker <Label, SelectionValue, Content>' initializer is unused"
            ForEach(cateName) { cate in
                Text(cate.cateName ?? "").tag(cate as CateEnt?)
            }
        }
    }
}
...

also added those lines in CatesEnt+ & FilesEnt+CoreDataProperties.swift files:

public var wrappedCateName: String {
    cateName ?? "unknown cates"
}


public var wrappedFileName: String {
    fileName ?? "unknown files"
}
public var wrappedFileCate: String {
    fileCate ?? "unknown files"
    }
public var catesArray: [CatesEnt] {
    let set = cates as? Set<CatesEnt> ?? []
    return set.sorted {
        $0.wrappedCateName < $1.wrappedCateName
    }
}

in another view, user enters cateName values that are shown as a list in the same order in Picker.

I am rockie learning SwiftUI. Thanks for help!