How to know the UITableview row number

Question

I have a UITableViewCell with UISwitch as accessoryview of each cell. When I change the value of the switch in a cell, how can I know in which row

Answer 1

Accepted solution is a clever hack.

However why do we need to use hitpoint if we can utilize already available tag property on UIView? You would say that tag can store only either row or section since its a single Int.

Well... Don't forget your roots guys (CS101). A single Int can store two twice-smaller size integers. And here is an extension for this:

extension Int {

    public init(indexPath: IndexPath) {
        var marshalledInt: UInt32 = 0xffffffff

        let rowPiece = UInt16(indexPath.row)
        let sectionPiece = UInt16(indexPath.section)
        marshalledInt = marshalledInt & (UInt32(rowPiece) << 16)
        marshalledInt = marshalledInt + UInt32(sectionPiece)

        self.init(bitPattern: UInt(marshalledInt))
    }

    var indexPathRepresentation: IndexPath {
        let section = self & 0x0000ffff

        let pattern: UInt32 = 0xffff0000
        let row = (UInt32(self) & pattern) >> 16
        return IndexPath(row: Int(row), section: Int(section))
    }
}

In your tableView(_:, cellForRowAt:) you can then:

cell.yourSwitch.tag = Int(indexPath: indexPath)

And then in the action handler you would can:

func didToogle(sender: UISwitch){
    print(sender.tag.indexPathRepresentation)
}

However please note it's limitation: row and section need to be not larger then 65535. (UInt16.max)

I doubt your tableView's indexes will go that high but in case they do, challenge yourself and implement more efficient packing scheme. Say if we have a section very small, we don't need all 16 bits to represent a section. We can have our int layout like:

{section area length}{all remaining}[4 BITS: section area length - 1]

that is our 4 LSBs indicate the length of section area - 1, given that we allocate at least 1 bit for a section. Thus in case of our section is 0, the row can occupy up to 27 bits ([1][27][4]), which definitely should be enough.