In Swift, Optional,? And! The relationship between

In Swift, Optional,? And! The relationship between

Optional <ClassName> equivalence with ClassName?

Yes, ClassName! forcing a value causes a crash ( if the object is nil, the value crashes )

imageview!. Image is a imageView forced unpacking, ImageView. image! is the forced unpacking of the image, and if it is found to be nil after unpacking, the crash

Apart from! And? , there is a kind of thing called nilliteralconvertible

'? ' must is followed by a call, member lookup, or subscript

Summary

1. Use a question mark? The object allows nil to appear, using an exclamation point! The object appears nil will crash

2. Use a question mark? Scenarios require content on the right side of the object, except when declared

3. Can I put a question mark? With an exclamation point! Understood as unpacking operations,? Support Package is empty, and! Crashes when the package is empty

In Swift, Optional,? And! The relationship between