How to change String Array to Int Array?

I would do this :

let myStringArray = ["12", "123", "45"]
var myIntArray = [Int]() // Initialize an empty array of Int
for s in myStringArray {
    if let val = Int(s){     // Int() will return nil if s is not a number string
         myIntArray.append(val)
     }
}
print(myIntArray)

Another way:

let myStringArray = ["12", "123", "45"]
let myIntArray = myStringArray.flatMap{Int($0)}
print(myIntArray)