Swift integer type cast to enum

Question

I have enum declaration.

enum OP_CODE {
    case addition
    case substraction
    case multiplication
    case division
}

And use it in a method:

func performOperation(operation: OP_CODE) {

}

We all know that how we can call this normally

self.performOperation(OP_CODE.addition)

But if I have to call it in some delegate where integer value is not predictable than how to call it.

For example:

func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
     self.delegate.performOperation(indexPath.row)
}

Here, Compiler throws an error Int is not convertible to 'OP_CODE'. Tried here many permutations. But not able to figure it out.

Answer 1

You need to specify the raw type of the enumeration

enum OP_CODE: Int {
    case addition, substraction, multiplication, division
}

addition will have a raw value of 0, substraction of 1, and so on.

and then you can do

if let code = OP_CODE(rawValue: indexPath.row) {
    self.delegate.performOperation(code)
} else {
   // invalid code
}

More info here: https://developer.apple.com/library/ios/documentation/swift/conceptual/Swift_Programming_Language/Enumerations.html#//apple_ref/doc/uid/TP40014097-CH12-XID_222

---

for older swift releases

In case you're using an older version of swift, raw enumerations work a bit different. In Xcode < 6.1, you have to use fromRaw() instead of a failable initializer:

let code = OP_CODE.fromRaw(indexPath.row)