Fast enumeration in OS 3.0

Question

I just tried compileing my iPhone app against OS 3.0 and I get a compile error when using fast enumeration.

I'm trying to go through an NSArray containing cComment classes:

for (cComment* newComment in comments.comments)

And I get this error

error: type of accessor does not match the type of property 'comments'.

This works flawlessly when compiled with OS 2.2.1.

I understand the error, the enumaretion isn't strongly typed but since as far as I know generics/templates are not supported in objective-c. So currently I can only see one way around this:

for (id commentObject in comments.comments)
{
     cComment *newComment = (cComment *)commentObject;
}

Can anyone think of another way? Why has this changed? Any points to apple documentation about this change would be appreciated.

EDIT

Following Grouchal suggestion i tried this: NSArray* allComments = comments.comments and I got the same error so it seems its not about the enumeration after all

here's the code form the header file:

NSMutableArray *comments;

@property (readonly,nonatomic) NSArray* comments;

and the property is synthesized in the implementation file.

Changing the property to NSMutableArray seems to solve the problem but I don't see any reason why this should be the case. Any ideas.

Thanks.

Answer 1

I don't see any reason why this code shouldn't work in OS 3.0 I have similar code working already.

What happens if you change the code to

NSArray *commentArray = comments.comments;
for (cComment *newComment in commentArray){
.....
}

I've just noticed as I've written this where the * is in your code - is this the problem? should it really be cComment* in the for declaration?

Answer 2

The problem is in the property definition. You should change have it as:

@property (readonly,nonatomic) NSMutableArray* comments

On the downside, your array will be exposed as mutable (though I suppose that's what you wanted to prevent).

Answer 3

I'm going to close this question and ask a new one under objective-c changes for iPhone OS 3.0.

I implemented the getter method myself to return an NSArray and it works just fine. Also changing the property to NSMutableArray works but it really isn't what I want to do.

I have no idea why this changed. This is an objective-c change and not an OS change. Also there is no mention of it in the documentation of changes between 2.2 API 3.0 API.

Thanks everyone for responding.