bparol/SwiftTips

Interesting things from Swift language

SwiftTips

Interesting things from Swift language

Optionals

Assign value only when current value is not nil

var maybe: Int? = nil
maybe? = 42
// maybe = nil
maybe = 7
maybe? = 42
// maybe = 42

Mapping optionals

let maybe: Int? = 7
let mappedMaybe = maybe.map { $0 * 6 }

Looping over non-nil values

let maybeValues: [Int?] = [1, 2,3,nil]
for case let value? in maybeValues {
    // here value is unwrapped, nil values are filtered out
}

// it's equivalent to:
for case let .some(value) in maybeValues {
  // 
}

// we can also loop over every nil in the array
for case let .none in maybeValues {
  // 
}

// or using shorthand
for case nil in maybeValues {
  // 
}

Comparing equality of optional and non-optional values

When comparing Optional vs Non-Optional Swift will promote Non-Optional to Optional in order to apply equality check on two Optionals.

let maybe7: Int? = 7
if maybe7 == 7 {
    print("it's seven!")
}