Update Firebase data in tableView cell on tap - ios

Question

I am using Firebase real time database to display posts in a tableView. I want to increase the number of likes of a specific post when the user double taps the corresponding cell.
I got the double tap working and am already printing out the correct indexPath.
override func viewDidLoad() {
super.viewDidLoad()
// double tap
let doubleTapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(handleDoubleTap(sender:)))
doubleTapGestureRecognizer.numberOfTapsRequired = 2
postTableView.addGestureRecognizer(doubleTapGestureRecognizer)
}
And here's what I tried according to the Firebase documentation to update the likes:
func handleDoubleTap(sender: UITapGestureRecognizer) {
let touchPoint = sender.location(in: postTableView)
if let indexPath = postTableView.indexPathForRow(at: touchPoint) {
print(indexPath)
let post = posts[indexPath.row]
let oldLikes = post.likes
let newLikes = oldLikes! + 1
let postUpdates = ["\(post.likes)": newLikes]
database.updateChildValues(postUpdates)
postTableView.reloadData()
}
}
It doesn't throw any errors but is not working.
This is the database structure:
And here's how I declared the database:
struct post {
let author : String!
let creationDateTime : String!
let content : String!
let likes : Int!
}
And in viewDidLoad
let database = FIRDatabase.database().reference()
This is how I create a post:
#IBAction func savePost(_ segue:UIStoryboardSegue) {
let addPostVC = segue.source as! AddPostViewController
let author = currentUser.displayName
let date = Date()
let formatter = DateFormatter()
formatter.dateFormat = "dd.MM.yyyy"
let dateResult = formatter.string(from: date)
let creationDateTime = "\(dateResult)"
let content = addPostVC.passTextContent
let likes = 0
let post : [String : AnyObject] = ["author" : author as AnyObject,
"content" : content as AnyObject,
"creationDateTime" : creationDateTime as AnyObject,
"likes" : likes as AnyObject]
database.child("Posts").childByAutoId().setValue(post)
}
And this how I retrieve the data in viewDidLoad
database.child("Posts").queryOrderedByKey().observe(.childAdded, with: {
snapshot in
let postID = (snapshot.value as? NSDictionary)?["postID"] as? String ?? ""
let author = (snapshot.value as? NSDictionary)?["author"] as? String ?? ""
let content = (snapshot.value as? NSDictionary)?["content"] as? String ?? ""
let creationDateTime = (snapshot.value as? NSDictionary)?["creationDateTime"] as? String ?? ""
let likes = (snapshot.value as? NSDictionary)?["likes"] as? Int ?? 0
self.posts.insert(post(postID: postID, author: author, creationDateTime: creationDateTime, content: content, likes: likes), at: 0)
self.postTableView.reloadData()
})

Answer 1

You have a problem with your database reference. When you do let database = FIRDatabase.database().reference() then you are refering to the main node in your database structure. This means that you will be working with the structure under the root in your database Json. The only child of it will be the Posts key.
When you do
let postUpdates = ["\(post.likes)": newLikes]
database.updateChildValues(postUpdates)
you are trying to update the value under the root node, which clearly does not exist. The only reference it can find is the key Posts.
In order to perform the update in the correct place, you could get child references from your main reference, especially one to the post you are interested in updating.
For example, you could do the following:
let postReference = database.child("Here goes the post Id").
Then, you will be able to use updateChildValues correctly on this new reference, since it will be updating the specific post.
Another thing that may be used wrong is the dictionary that is being sent to the updateChildValues. The structure of the dictionary that you have to provide is the following:
["key that you want to update": new value]
So in your case, instead of providing the previous like count and the new like count, you should provide a dictionary as the following:
let postUpdates = ["likes": newLikes]