Default address book request message
Default address book request message

If you want to show the user a custom message when asking for permission to use their contacts or address book, instead of the default one shown above, you need to add this field to your Info.plist file:

NSContactsUsageDescription

with the value being the text you want displayed. An example would be

“We would like to use your contacts to find out which of your friends are using Instagram!”

More info here: Apple Developer Documentation