All of the punctuation in Swift looked pretty weird to me until recently, but now that I get it, I’ve really learned to appreciate how great the syntax actually is. The way I think of it is this: if you’re using ?, you’re asking a question, and when you use ! you’re asserting that you already have the answer. Of course, for the second case, you need do need to be sure or your app will blow up.
So, for example:
Asking a Question
if let foo = dictionary[“foo”] as? String { … }
Is the value for the key “foo” a string? If so, assign it to the constant foo.
delegate?.objectDidSomething(self)
Do I have a delegate, and can it respond to objectDidSomething:?
Making an Assertion
managedObjectContext!.save(&error)
I know that managedObjectContext is not nil.
let foo = bar as! String
I know bar is a string, so nothing will go wrong casting it.
