Providing a default value for an Optional in Swift?

Question

The idiom for dealing with optionals in Swift seems excessively verbose, if all you want to do is provide a default value in the case where it's nil:

if let value = optionalValue {
    // do something with 'value'
} else {
    // do the same thing with your default value
}

which involves needlessly duplicating code, or

var unwrappedValue
if let value = optionalValue {
    unwrappedValue = value
} else {
    unwrappedValue = defaultValue
}

which requires unwrappedValue not be a constant.

Scala's Option monad (which is basically the same idea as Swift's Optional) has the method getOrElse for this purpose:

val myValue = optionalValue.getOrElse(defaultValue)

Am I missing something? Does Swift have a compact way of doing that already? Or, failing that, is it possible to define getOrElse in an extension for Optional?

Answer 1

Update

Apple has now added a coalescing operator:

var unwrappedValue = optionalValue ?? defaultValue

---

The ternary operator is your friend in this case

var unwrappedValue = optionalValue ? optionalValue! : defaultValue

You could also provide your own extension for the Optional enum:

extension Optional {
    func or(defaultValue: T) -> T {
        switch(self) {
            case .None:
                return defaultValue
            case .Some(let value):
                return value
        }
    }
}

Then you can just do:

optionalValue.or(defaultValue)

However, I recommend sticking to the ternary operator as other developers will understand that much more quickly without having to investigate the or method

Note: I started a module to add common helpers like this or on Optional to swift.