leaving textfields blank - crash - swift 4

Question

I am trying to create a course avg calculator with textfields. However if I only want to enter in a few marks (i.e. not filling out all the textfields) I get a crash.

I get this error:

Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value

In my code, I tried to avoid this nil value, but I get the error on that first line if I leave the first textfield blank. I do further calculations with these textfields, so I'm not sure if I will get similar errors once I fix these lines.

    if b?.text != nil {
        b?.text = String(Double(b!.text!)!/100)
    }
    if d?.text != nil {
        d?.text = String(Double(d!.text!)!/100)

    }
    if f?.text != nil {
        f?.text = String(Double(f!.text!)!/100)
    }
    if h?.text != nil {
        h?.text = String(Double(h!.text!)!/100)
    }

From docs (about `text` property of `UITextField`): This string is @"" by default. So even if `text` property is of type `String?` in most cases it's not `nil`. Maybe better for you would be checking if `text` isn't empty: `if !textField.text.isEmpty` — Robert Dresler, Dec 06 '18 at 20:53

Shehata Gamal · Answer 1 · 2018-12-06T19:57:05.760

0

Force unwrap the double conversion

Double(b!.text!)!

is the reason as empty string can't be converted to double so it returns nil and as you use ! , hence the crash , you need

if let tex = b , content = tex.text ,  value = Double(content) {
   print(value)
}

Also don't make the b var an optional make it !

 var b:UITextField! // and make sure you init it

Edit: Don't create other vars to hold instance ones use them directly

@IBOutlet weak var weight1: UITextField!

if let content = weight1.text ,  value = Double(content) {
   print(value)
   weight1.text = "\(value/100)"
}

edited Dec 06 '18 at 19:57

answered Dec 06 '18 at 19:44

Shehata Gamal

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so write `if let b?.text = String(Double(b!.text!)!/100)` – MontgommeryJR Dec 06 '18 at 19:46
I have `@IBOutlet weak var weight1: UITextField!` and `let var b = weight1` – MontgommeryJR Dec 06 '18 at 19:51

score 0 · Answer 2 · answered Dec 29 '18 at 21:55

Double(b!.text!)!

This is the reason, your input text (b!.text!) is not convertible to double hence ended up with nil.

for ex: you might be giving input "12Th45", this is not convertible to double.

Always use optional binding wherever you are not sure that value is there or not.

Thanks.

leaving textfields blank - crash - swift 4

2 Answers2