I have a tableview that the user edits information in using textfields, and I store that information into an array that keeps track of all the values. The issue occurs when the user scrolls back to a cell they already edited and the values the added previously are now values from other cells.

I understand that cells are reused, and as a result their data needs to be updated whenever they are being viewed again. I also learned that cellforrowat is called every time a cell is loaded into the view as opposed to just the first time a cell is created. I made a test project to figure out my problem.

My first attempt at solving the problem went like so

1. cellforrowat is called
2. if this is the first time the cell is being made set default values and add its data to the array keeping our cell data
3. If this is not the first time, draw information from the data source at indexpath.row and apply it to the cell

if cellInformation.count < (indexPath.row   1) // Newly made cell
        {
            cell.value = 0
            cell.tField.text = ""
            
            cellInformation[cellInformation.count] = cell
            
        }
        else if (cellInformation.count >= indexPath.row) // Cell we've seen before
        {
            cell.configure(Value: cellInformation[indexPath.row]!.value) // Sets the          textField.text to be the same as the cells value
        }

This worked better but when I scrolled back to the top of my tableview, the top most cells were still getting random data. My next attempt generated an ID tag for each cell, and then checking if the id tag of the cell at cellforrowat matched any of the one's in the array.

        if cellInformation.count < (indexPath.row   1) // 0 < 1
        {
            cell.idTag = idTagCounter
            idTagCounter  = 1
            
            cell.value = 0
            cell.tField.text = ""
            
            cellInformation[cellInformation.count] = cell
        }
        else if (cellInformation.count >= indexPath.row)
        {
            for i in 0...idTagCounter - 1
            {
                if(cell.idTag == cellInformation[i]?.idTag)
                {
                    cell.configure(Value: cellInformation[i]!.value)
                }
            }
            cell.configure(Value: cellInformation[indexPath.row]!.value)
        }

This got pretty much the same results as before. When I debugged my program, I realized that when i scroll down my tableview for the first time, indexPath.row jumps from a value like 7 down to 2 and as I scroll more and more, the row goes further away from what it should be for that cell until it eventually stops at 0 even if there are more cells i can scroll to. Once the row hits 0, cellforrowat stops being called.

Any ideas on how i can accurately assign a cells values to the information in my array?

CodePudding user response：

Your premise is wrong:

cellforrowat is called

if this is the first time the cell is being made set default values and add its data to the array keeping our cell data

If this is not the first time, draw information from the data source at indexpath.row and apply it to the cell

You should set up a model object that contains the data for the entries in your table view, and your cellForRowAt() method should fetch the entry for the requested IndexPath.

Your model can be as simple as an array of structs, with one struct for each entry in your table. If you use a sectioned table view you might want an array of arrays (with the outer array containing sections, and the inner arrays containing the entries for each section.)

You should not be building your model (array) in calls to cellForRowAt().

You also should not, not NOT be storing cells into your model. You should store the data that you display in your cells (text strings, images, etc. Whatever is appropriate for your table view.)

Assume that cellForRowAt() can request cells in any order, and ask for the same cells more than once.

Say we want to display an array of animals, and a numeric age:

struct Animal {
   let species: String
   let age: Int
}

//Create an array to hold our model data, and populate it with sample data
var animals: [Animal] = [
    Animal(species: "Lion", age: 3),
    Animal(species: "Tiger", age: 7),
    Animal(species: "Bear", age: 4)
]

//...

func cellForRow(at indexPath: IndexPath) -> UITableViewCell? {
    let cell = dequeueReusableCell(withIdentifier: "cell" for: indexPath)
    let thisAnimal = animals[indexPath.row]
    cell.textLabel.text = "\(thisAnimal.species). Age = \(thisAnimal.species)"
}

Note that for modern code (iOS >=14), you should really be using UIListContentConfigurations to configure and build your cells.