Swift：无法从字符串转换为int（使用滑块标记）

Question

let device = devices[indexPath.row]
let deviceTag = device["deviceID"] as? String
cell.slider.tag = deviceTag

I get an error from the above: Cannot assign value of type 'String?' to type 'Int'

This doesn't work (below):

cell.slider.tag = Int(deviceTag)

or what "fix-it" provides:

cell.slider.tag = Int(deviceTag!)!

Answer 1

You need to set optional while casting from string. Try the below code.

let device = devices[indexPath.row]
let deviceTag = device["deviceID"] as! String
cell.slider.tag = Int(deviceTag)

Answer 2

Unless you're 100% sure the value of the dictionary device is an Int you shouldn't implicitly unwrap those optionals.

You can use:

if let deviceTag = deviceTag, tag = Int(deviceTag) { cell.slider.tag = tag }

or

cell.slider.tag = Int(deviceTag) ?? 0

But looking at your examples, it seems like deviceTag isn't a number at all. Perhaps you should look in your debug area (left panel) to see what the value is or simply print(deviceTag) to see what the value is.