Array index out of range when populate tableview from Firebase database

Question

    let ref = Database.database().reference(withPath: "items")
            ref.observe(.value) { (snapshot) in
                guard let dict = snapshot.value as? NSArray else { return }
                let decoder = JSONDecoder()
                decoder.keyDecodingStrategy = .convertFromSnakeCase
                dict.forEach { (value) in
                    do {

                        let itemData = try JSONSerialization.data(withJSONObject: value,options: .prettyPrinted)
                        let item = try decoder.decode(Item.self, from: itemData)
                            self.items.append(item)
                    }
                    catch let err {
                    print(err.localizedDescription)
                    }
                }
print(self.items) // This 
print(self.items[0]) // works 
            }

and trying to access items in tableview:

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
itemType = String(describing: (self.items[indexPath.section].item_type)) // terminating with index out of range error
            //...
    }

The error occurs because the observe methods work asynchronously and executes later then tableview populates data.

How to solve this ?

how you are returning number of sections for UITableViewDataSource? — Muhammad Afzal
– Muhammad Afzal, Commented Feb 26, 2020 at 5:15
@Muhammad Afzal for now its constant int for testing purpose func numberOfSections(in tableView: UITableView) -> Int { return 3 } — Jay
– Jay, Commented Feb 26, 2020 at 5:20
that's the main reason your app crashing you need to return items.count in numberof section of you want to use sections if you want to use rows return number of rows. — Muhammad Afzal
– Muhammad Afzal, Commented Feb 26, 2020 at 5:22

user6248853 · Accepted Answer · 2020-02-26 05:16:40Z

1

You need something like this:::

let ref = Database.database().reference(withPath: "items")
        ref.observe(.value) { (snapshot) in
            guard let dict = snapshot.value as? NSArray else { return }
            let decoder = JSONDecoder()
            decoder.keyDecodingStrategy = .convertFromSnakeCase
            dict.forEach { (value) in
                do {

                    let itemData = try JSONSerialization.data(withJSONObject: value,options: .prettyPrinted)
                    let item = try decoder.decode(Item.self, from: itemData)
                        self.items.append(item)
                }
                catch let err {
                print(err.localizedDescription)
                }
            }

            self.yourtableView.reloadData()

            print(self.items) // This 
             print(self.items[0]) // works 
        }

And you need to implement numberOfRows at index path method

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

and return items.count there.

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

     itemType = String(describing: (self.items[indexPath.row].item_type)) // terminating with index out of range error
        //...
}

answered Feb 26, 2020 at 5:16

user6248853

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1 Comment

user6248853 Over a year ago

@Jay Good.. but pay attention also to whether you want to use rows as the repeating entity or the sections in your table view.

Muhammad Afzal · Accepted Answer · 2020-02-26 05:25:28Z

1

if you want to use numberofsections

func numberOfSections(in tableView: UITableView) -> Int {
        return items.count
  }
 func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
itemType = String(describing: (self.items[indexPath.section].item_type)) 
    }

if you want to use numberofrows

func numberOfSections(in tableView: UITableView) -> Int {
        return 1
  }
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return items.count
    }
 func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
itemType = String(describing: (self.items[indexPath.row].item_type)) 
    }

answered Feb 26, 2020 at 5:25

Muhammad Afzal

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