在第二个视图控制器上获取文档参考

Question

Would anyone be able to help so that when a user clicks on a customer name (using a table view) that their details will appear on the second view controller(VC). I think it is because I haven't pulled the documentID through to this. I've tried adding in documentID into Second VC .document(documentID)

Initial VC code

    var customerList = [CustomerLsModel]()
    override func viewDidLoad() {
            super.viewDidLoad()
            let db = Firestore.firestore()

            db.collection("customers").getDocuments() { (snapshot, error) in
                if let error = error{
                    print("Can't get customers: \(error)")
                    let alert = UIAlertController(title: "Error", message: "There was an issue in pulling your information. Please close the application and try again.", preferredStyle: .alert)
                    alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
                    self.present(alert, animated: true)
                } else {
                    for document in snapshot!.documents{
                        let firstname = document["firstname"]
                        let lastname = document["lastname"]
                        let address = document["address"]
                        let customer = CustomerLsModel(firstname: firstname as! String?, lastname: lastname as! String?, address: address as! String?)

                        self.customerList.append(customer)
                        self.orderAndLimit()
                    }
                    self.customerTable.reloadData()
                }
            }
        }
    }

Second VC

   let db = Firestore.firestore()
    db.collection("customers").document().getDocument { (document, Error) in
        if let document = document, document.exists{
            self.firstNameLabel.text = document.get("firstname") as? String
        }
    }

This is my customer model class

    class CustomerLsModel{
        var firstname: String!
        var lastname: String?
        var address: String?

        init(firstname: String?, lastname: String?, address: String?){
            self.firstname = firstname
            self.lastname = lastname
            self.address = address
        }

Answer 1

According to Firebase documentation for Swift if you use method document() without path parameter you are creating DocumentReference to new document. So when you try getDocument on this reference - it's empty.

Only if you add path in parameter you will get data from existing document.

I hope it will help!

Answer 2

The answer will really depend on how you want to work with the data but here's two ways. But your instinct is correct - you'll need to keep track of the customers documentId.

So you could do this when reading the customers from Firestore and pass in all of the strings and documentId to populate each object

class CustomerLsModel{
   var firstname: String!
   var lastname: String?
   var address: String?
   var docId: String!

   init(firstname: String?, lastname: String?, address: String?, docId: String) {
      self.firstname = firstname
      self.lastname = lastname
      self.address = address
      self.documentId = docId
   }
}

or this, which makes the code a bit simpler by passing in the Firestore snapshot

class CustomerLsModel {
   var firstname: String?
   var lastname: String?
   var address: String?
   var docId: String!

    init(withDoc: QueryDocumentSnapshot) {
        self.docId = withDoc.documentID
        self.firstname = withDoc.get("first_name") as? String ?? "no first"
        self.lastname = withDoc.get("last_name") as? String ?? "no last"
        self.address = withDoc.get("addres") as? String ?? "no address"
    }
}

from there, when a user selects a customer, you could either pass that object to the detail view controller for display or, just pass the docId and use that in your child viewController to read the data from Firestore.

There are about 100 ways to 'pass' data - a Segue is a popular choice you could also set a 'customer' var in the detail viewController or the detail could read the data from the master. It really depends on your use case.