Cannot invoke initializer for type 'Double' with an argument list of type '(String?)'

Question

I have two issues:

let amount:String? = amountTF.text

1. amount?.characters.count <= 0

It\'s giving error

Answer 1

Another reason for the error is amount it should not be null

let am = Double(amount!)

with check contol

if amount != nil {
   let am = Double(amount!)
}