What does an exclamation mark mean?
Swift uses exclamation marks to signal both force unwrapping of optionals and explicitly unwrapped optionals. The former means "I know this optional variable definitely has a value, so let me use it directly." The latter means "this variable is going to be nil initially then will definitely have a value afterwards, so don't make me keep unwrapping it."
Broadly speaking, using exclamation marks is frowned upon because "trust me it's safe" isn't as good as the compiler absolutely enforcing it. That being said, it's your code: if you know something cannot be nil (usually because if it were nil your program would explode!) then do what works best.
Available from iOS 7.0 – see Hacking with Swift tutorial 1
Did this solution work for you? Please pass it on!
Other people are reading…
- How to split an array into chunks
- How to conform to the Hashable protocol
- How to use map() with an optional value
- How to create an Objective-C bridging header to use code in Swift
- How to find the first matching element in an array
About the Swift Knowledge Base
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
