Question

In Objective-C, I’ve seen, for example:

UIPickerView *tweetPicker

and

UIPickerView* tweetPicker

What does the asterisk mean (I know, the first part is a dupe…) and why does it go on different parts of the declaration in different contexts?

Answer 1

In the exact case you’re showing, there is no difference. Some people like to think of tweetPicker being of type UIPickerView *, that is, a pointer to a UIPickerView. These people usually write it as

UIPickerView* tweetPicker;

Other people prefer to think of it like *tweetPicker is a UIPickerView, that is, dereferencing the pointer gives a UIPickerView. Those people usually write:

UIPickerView *tweetPicker;

I prefer the latter, because the C (and Objective-C because of that) syntax supports it better. Take, for example, the following variable declarations:

int* a, b, c;
int  *a, *b, *c;

At first glance, the novice C (or Objective-C) programmer might say “those are the same”, but they’re not. In the first case, b and c are regular integers, in the second case, they’re pointers. a is a pointer in both cases.

From my perspective, the concept of a “type” is so weak in C anyway (what with the behaviour of typecasting and the like) that extending that concept one step further to pointer variables is crazy – especially with the automatic & silent conversions to and from void * or id that you get.