Like regular optionals, implicitly unwrapped optionals might contain a value or they might be
nil. However, unlike regular optionals you don’t need to unwrap them in order to use them: you can use them as if they weren’t optional at all.
Implicitly unwrapped optionals are created by adding an exclamation mark after your type name, like this:
let age: Int! = nil
Because they behave as if they were already unwrapped, you don’t need
if let or
guard let to use implicitly unwrapped optionals. However, if you try to use them and they have no value – if they are
nil – your code crashes.
Implicitly unwrapped optionals exist because sometimes a variable will start life as nil, but will always have a value before you need to use it. Because you know they will have a value by the time you need them, it’s helpful not having to write
if let all the time.
That being said, if you’re able to use regular optionals instead it’s generally a good idea.