Swift - Checking unmanaged address book single value property for nil
问题 I'm relative new to iOS-Development and swift. But up to this point I was always able to help myself by some research on stackoverflow and several documentations and tutorials. However, there is a problem I couldn't find any solution yet. I want to get some data from the users addressbook (for example the single value property kABPersonFirstNameProperty ). Because the .takeRetainedValue() function throws an error if this contact doesn't have a firstName value in the addressbook, I need to