Firestore : How can I get whole data in Firestore?

Question

This ViewModel is about saving data in Firestore with specific data types.

    import Foundation
    import Firebase
    import FirebaseStorage
    import FirebaseStorageSwift
    import UIKit
    
    class UploadViewModel : ObservableObject {
        
        @Published var loading : Bool = false
        
        func storeImageWithUrl(images : [UIImage], completion : @escaping (_ urls : [String]) -> ()) {
            
            self.loading = true
            
            var count = 0
            var urls : [String] = []
            
            for image in images {
                
                let ref = Storage.storage().reference(withPath: UUID().uuidString)
                
                guard let imageData = image.jpegData(compressionQuality: 0.5) else {return}
                
                ref.putData(imageData, metadata: nil) { metaData, error in
                    if let error = error {
                        print("failed to push image cause of error")
                        return
                    }
                    
                    ref.downloadURL { url, error in
                        if let error = error {
                            print("error to make url")
                            return
                        }
                        guard let url = url else {return}
                        count += 1
                        urls.append(url.absoluteString)
                        
                        if count == images.count {
                            completion(urls)
                        }
                    }
                }
            }
        }
        
        func storeItemInformation(title : String, description : String, category : String, contactInfo : String, price : String, imageUrls : [String], timeStamp : Date = Date(), saved : Bool = false, seller : String, completion : @escaping (_ result : Bool) -> ()) {
            
            let uid = AuthService.instance.makeUid()
            
            guard let userData = ["title": title, "description" : description, "category" : category, "price" : price, "imageURL" : imageUrls, "timestamp" : timeStamp, "contactInfo" : contactInfo, "saved" : saved, "seller" : seller] as? [String : Any] else { return }
            
            Firestore.firestore()
                .collection("Wholeitems")
                .document(category)
                .collection(uid)
                .document(title)
                .setData(userData) { error in
                    if let error = error {
                        print("Error to save whole Data")
                        completion(false)
                        return
                    }
                    print("Success to save whole data")
                    self.loading = false
                    completion(true)
            }
        }
    }

Below code is about fetching data from Firestore with ItemModel.

    import Foundation
    import SwiftUI
    import Firebase
    import FirebaseAuth
    
    class FeedViewModel : ObservableObject {
        
        @Published var feeds : [ItemModel] = []
        
        init() {
            fetchItems()
            print(feeds)
        }
        
        func fetchItems() {
            
            Firestore.firestore()
                .collection("Wholeitems")
                .getDocuments { snapshot, error in
                    if let error = error {
                        print("error to get data")
                        return
                    }
                    
                    if let snapshot = snapshot {
                        DispatchQueue.main.async {
                            self.feeds = snapshot.documents.map({ d in
                                return ItemModel(id: d.documentID,
                                                 category: d["category"] as? String ?? "",
                                                 contactInfo: d["contactInfo"] as? String ?? "",
                                                 description: d["description"] as? String ?? "",
                                                 price: d["price"] as? String ?? "",
                                                 timestamp: d["timestamp"] as? String ?? "",
                                                 title: d["title"] as? String ?? "",
                                                 saved : d["saved"] as? Bool ?? false,
                                                 seller: d["seller"] as? String ?? "",
                                                 imageURL: d["imageURL"] as? [String] ?? []
                                )
                            })
                        }
                    }
                }
        }
    }

The problem is that I don't know why the feeds array is empty.

I tried to get all of the documents in the Firestore collection named Wholeitems. But, the array is empty.

Could you help me? Thanks!