CODEWITHSUNDEEP
iosswift
Jan Mark Dannenberg
Jan Mark Dannenberg

Reputation: 703

Trying to avoid finding nil unwrapping optional values

I am trying to do some math with user input numbers I get from UITextFields. The problem, there could be nothing in the TextField, in that case the value should be set to zero. I tried the guard statement but it seems I use it the wrong way:

    guard let number = numberTextField.text else{ let number = 0}

What is wrong with this code? What should I change?

Upvotes: 0

Views: 84

Answers (3)

Blake
Blake

Reputation: 107

You'll want to use a default value instead of a guard to get the behavior you desire.

let number = Double(numberTextField.text) ?? 0

Upvotes: 0

Charles Srstka
Charles Srstka

Reputation: 17040

The guard statement cannot be used, because it requires you to exit from the function if the condition is false. Instead, you should use the ?? operator:

let number = numberTextField.text.flatMap { Int($0) } ?? 0

Why flatMap? Because we need to convert the String to an Int (or a Double, if this may contain a floating-point value) in order for it to be the same type as the 0. flatMap on an optional returns the value inside the closure if text is not nil, but returns nil if it is. In either case you'll end up with an optional Int, which is then made non-optional by supplying the default value of 0 via the ?? operator.

Upvotes: 4

Tung Nguyen
Tung Nguyen

Reputation: 104

Nothing means empty string rather than nil "guard let" is used to check nil value

Let try the method below

if numberTextField.text.isEmpty {
   let number = 0
}

Upvotes: -1

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