Firebase Child must be a non-empty string and not

Question

I am coding a basic messaging app in Swift with Firebase. I am done with the majority of the app but in the ChatViewController Im getting this error message:

*** Terminating app due to uncaught exception 'InvalidPathValidation', reason: '(child:) Must be a non-empty string and not contain '.' '#' '$' '[' or ']''
*** First throw call stack:

My ChatViewController code is:

import UIKit
import Firebase

struct Post {
    let messageTextt: String!
}

class ChattViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

let database = DatabaseReference!.self
@IBOutlet weak var messageText: UITextField!
@IBOutlet weak var tableViewC: UITableView!


var posts = [Post]()


override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.

    tableViewC.delegate = self
    tableViewC.dataSource = self

    let database = Database.database().reference()
    database.child("Posts").child(currentUserChatId).queryOrderedByKey().observe(.childAdded, with: {

        snapshot in

        let messageTextt = (snapshot.value as? NSDictionary)?["messageTextt"] as? String ?? ""
        self.posts.insert(Post(messageTextt : messageTextt), at: 0)
        self.tableViewC.reloadData()

    })



}




@IBAction func sendMessageText(_ sender: Any) {
    if messageText.text != "" {
        let uid = Auth.auth().currentUser?.uid
        let database = Database.database().reference()
        let bodyData : [String : Any] = ["uid" : uid!, "messageTextt" : messageText.text!]
        database.child("posts").child(currentUserChatId).childByAutoId().setValue(bodyData)
    }
}


    func tableView(_ tableView: UITableView, numberOfRowsInSection
        section: Int) -> Int {
        return posts.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt IndexPath:
        IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: IndexPath)
        let messageTextt = cell.viewWithTag(1) as! UITextView
        messageTextt.text = posts[IndexPath.row].messageTextt
        return cell
    }

I have tried looking for other users with the same problem but I haven't managed to solve it so far.

Answer 1

The answer can be extracted from the crash log you're receiving. But first, here's a little tip for debugging:

Add an exception breakpoint

Going on, it is certain that your currentUserChatId has an invalid value. Try hard-coding it (ex. "someId") and see the result. Make sure it is defined and contains a valid value. Define it in your ChattViewController class.