What does an exclamation mark mean?
Swift version: 5.4
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.
SPONSORED From August 2nd to 8th you can join a FREE crash course for mid/senior iOS devs who want to achieve an expert level of technical and practical skills – it’s the fast track to being a complete senior developer!
Sponsor Hacking with Swift and reach the world's largest Swift community!
Available from iOS 7.0 – see Hacking with Swift tutorial 1
Similar solutions…
- What does weak mean?
- What does the message "Simulator user has requested new graphics quality: 100" mean?
- What does override mean?
- What does unowned mean?
- How to mark content as private using privacySensitive()
About the Swift Knowledge Base
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
