IOS apprentice

1. generics: meaning that they are independt of the type of thing you want to store inside these collections

2. optional

var checklistToEdit: Checklist?

3. Binding/ unwrapping: you cannot use optional variable directly, you must always test whether it has a value or not.

if let checklist = checklistToEdit {
 // “checklist” now contains the real object
} else {
 // the optional was nil
}

sfafads