No exact matches in call to initializer error message in swift

Question

I'm confused. Could someone please tell me why I get a "No exact matches in call to initializer" error when I have this code....

    let bill = textField.text
    let billTotal = Double(bill)

but when I force unwrap textField.text the error goes away and everything is good...

    let bill = textField.text!
    let billTotal = Double(bill)

My thinking is that it should still work without force unwrapping but the app will crash if the textField is nil.

Also, why can I not use an optional instead of force unwrapping?

 let bill = textField.text?
 let billTotal = Double(bill)

Using an optional gives me the same error: "No exact matches in call to initializer"

Answer 1

The error occurs because text is an optional and the initializer parameter must be non-optional.

My thinking is that it should still work without force unwrapping but the app will crash if the textField is nil.

In this case force unwrapping is fine because the text property of a UITextField is never nil although it's declared as optional.

But instead you should check the created Double because the entered text might be not convertible to Double, either with a default value

let billTotal = Double(textField.text!) ?? 0.0

or providing a more advanced error handling

if let billTotal = Double(textField.text!) {
    // do something with billTotal
} else {
    // handle the error
}

Answer 2

textField.text already an optional.. you can do

 if let bill = textField.text {
      let billTotal = Double(bill)
      }

Also you can do that by suggested By @Jessy Thanks ...

let billTotal = textField.text.flatMap(Double.init)

To convert in Double .. its inializer takes S : StringProtocol which confirm StringProtocol ... Only the String and Substring types in the standard library are valid conforming types not Optional String