Objective C Incompatible block pointer types sending

Question

I'm using parse 1.7.4 , this is y code :

+(NSArray *)getCategorieFromParse{



    PFQuery *categoriesQuery = [PFQuery queryWithClassName:@"Categorie"]; 

    [categoriesQuery findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error){ 

        if (!error) 

            return objects; 

        else 

            return [[NSArray alloc] init]; 

    }]; 




}

but this is generate this error :

Incompatible block pointer types sending 'NSArray *(^)(NSArray *__strong, NSError *__strong)' to parameter of type 'PFArrayResultBlock __nullable' (aka 'void (^)(NSArray * __nullable __strong, NSError * __nullable __strong)')

At the return line

Pretty much a duplicate here. Different framework, same problem. http://stackoverflow.com/q/29500188/620197 — Mike D, May 27 '15 at 14:01

score 3 · Accepted Answer · answered May 27 '15 at 14:00

Your block wasn't declared with a return type, and it returns an NSArray*, there it is a block returning an NSArray*. The method you are calling expects a block returning void. Obviously your block is not acceptable.

I suspect there is some deep misunderstanding going on what this block is supposed to do. Your method getCategorieFromParse cannot return an array. It's sending an asynchronous request, and your callback block will be called long after getCategorieFromParse returns. The callback block shouldn't try to return anything; it's job is to process the array that it was given.

score 2 · Answer 2 · edited May 23 '17 at 12:15

2

You cannot return values from within a code block. You should rather use a delegate (just an example I found on google) instead.

edited May 23 '17 at 12:15

Community

1
1

answered May 27 '15 at 13:50

Shai

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score 1 · Answer 3 · answered May 27 '15 at 14:01

You make asynchronous calls. You can't return array synchronously.

Solution: make your method also asynchronous:

+(void) getCategorieFromParse:(void (^)(NSArray*))completion
{
    PFQuery *categoriesQuery = [PFQuery queryWithClassName:@"Categorie"]; 

    [categoriesQuery findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error){ 

        if (!error) 

           completion(objects); 

        else 

           completion([[NSArray alloc] init]); 

    }]; 
}

Objective C Incompatible block pointer types sending

3 Answers3