Difficulty appending array of arrays in swift for tableview

Question

I am trying to build a tableview from some data that I have but I have come across some appending behaviour that I don't understand.

To debug I am trying this , if I say :

var sectionHeaders:[String] = ["0","1"]
var items:[[String]] = [["zero","zero","zero"],["one","one","one"]]

and display this in my tableview, I see a header "0" with three rows of zero, another header "1" with three rows of "one". Which is to be expected. However if I try and build the same structure using append, I get strange results :

var sectionHeaders:[String] = []
var items:[[String]] = [[]]
var tempItems:[String] = []

sectionHeaders.append("0")

        tempItems.append("zero")
        tempItems.append("zero")
        tempItems.append("zero")

        items.append(tempItems)

        tempItems = []

        sectionHeaders.append("1")

        tempItems.append("one")
        tempItems.append("one")
        tempItems.append("one")

        items.append(tempItems)

With this I get a section header of "0" with zero rows (no lines), and a header of "1" with three rows of zeros.

The data seems to be offset somehow

Is there something wrong with the way I am appending ?

My data source delegates are very simple :

    override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        
        return sectionHeaders[section]
    }
    
    
    override func numberOfSections(in tableView: UITableView) -> Int {
        
        return sectionHeaders.count
    }


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

    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        
        let cell = tableView.dequeueReusableCell(withIdentifier: "testCell", for: indexPath)
        
        let text = items[indexPath.section][indexPath.row]
        
        cell.textLabel?.text = text
        
        return cell
    }

   
}

Instead of using arrays of arrays, you should use an array of Structs. Within each Struct you can an array. This makes it easier to keep track of. — aheze
– aheze, Commented Apr 5, 2021 at 20:18
Thanks, but how would a struct look for something like this ? I can't visualize it. — jat
– jat, Commented Apr 6, 2021 at 12:41

jnpdx · Accepted Answer · 2021-04-05 20:19:02Z

1

When you do this:

var items:[[String]] = [[]]

You're defining items as being an array (the outer set of brackets) with one element, which is an empty array: [] (the inner set of brackets).

To not get the offset, it should be this:

var items:[[String]] = []

(just an empty array)

answered Apr 5, 2021 at 20:19

jnpdx

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1 Comment

jnpdx Over a year ago

Sure. When you are able, please mark the answer as correct by using the green checkmark.

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