Question

I am trying to understand the meaning of that “something” before the method name in objC. Here an example:

- (BOOL)peoplePickerNavigationController:(ABPeoplePickerNavigationController *)peoplePicker 
      shouldContinueAfterSelectingPerson:(ABRecordRef)person 
                                property:(ABPropertyID)property 
                              identifier:(ABMultiValueIdentifier)identifier

The method name is shouldContinueAfterSelectingPerson, the method has three parameter and has a return value (BOOL) but what is the role of peoplePickerNavigationController:(ABPeoplePickerNavigationController *)?

It isn’t the return value, it isn’t the method parameter (because cames before the method name), and so what is it?

Answer 1

In objective c the method is split up into 4 components (or so I would guess as this is how I see it)

I’ll break up this method:

- (BOOL)peoplePickerNavigationController:(ABPeoplePickerNavigationController *)peoplePicker 
      shouldContinueAfterSelectingPerson:(ABRecordRef)person 
                                property:(ABPropertyID)property 
                              identifier:(ABMultiValueIdentifier)identifier

the - signifies that it’s an instance method, you need to allocate an instance of this class to use it.

the (BOOL) signifies that it should return a BOOL, YES or NO.

the method is defined by a selector uid, peoplePickerNavigationController:shouldContinueAfterSelectingPerson:property:identifier:

That is the full method name unlike what you have said.

the last part are the parameters. Those are pretty self explanatory.