objective-c Completion Block issue - ios

Question

I am trying to get a JSON (NSString *) of the address book , in async task , however I want it to be asynchronously and with a completion block .
I have managed to retrieve that easy without the completion block , however when I am adding the completion block I have the following compiler error :
Incompatible block pointer types passing NSString *(^)(bool, CFErrorRef)' to parameter of type 'ABAddressBookRequestAccessCompletionHandler' (aka 'void (^)(bool, CFErrorRef)')
here is my code
+ (NSString *) getAddressBook:(id (^)())block {
ABAuthorizationStatus status = ABAddressBookGetAuthorizationStatus();
if (status == kABAuthorizationStatusDenied)
{
// if you got here, user had previously denied/revoked permission for your
// app to access the contacts, and all you can do is handle this gracefully,
// perhaps telling the user that they have to go to settings to grant access
// to contacts
[[[UIAlertView alloc] initWithTitle:nil message:#"This app requires access to your contacts to function properly. Please visit to the \"Privacy\" section in the iPhone Settings app." delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil] show];
return nil;
}
CFErrorRef error = NULL;
ABAddressBookRef addressBook = ABAddressBookCreateWithOptions(NULL, &error);
if (error)
{
NSLog(#"ABAddressBookCreateWithOptions error: %#", CFBridgingRelease(error));
if (addressBook) CFRelease(addressBook);
return nil;
}
if (status == kABAuthorizationStatusNotDetermined)
{
// present the user the UI that requests permission to contacts ...
ABAddressBookRequestAccessWithCompletion(addressBook, ^(bool granted, CFErrorRef error) -> THE ERROR OCCURS HERE !
{...
I think the problem is within my completion blocks , but I can't find some good example/tutorial for my specific issue I would be really glad if some 1 could help me please.

Answer 1

Your problem is that you are declaring getAddressBook like this(if we strip block)
-(id)block
And you are trying to pass it as a function of type:
-(void)block:(BOOL)aBool error:(CFErrorRef*)error
Blocks are quite hard to get used with syntax(which is improved in swift) however I'm always refering to this site when not sure:
block syntax reference
UPDATE:
You have to actually wait for your async method finish. You may also refer to official documentation
+ (void) getAddressBook:((^)(NSString* result))block {
ABAuthorizationStatus status = ABAddressBookGetAuthorizationStatus();
if (status == kABAuthorizationStatusDenied)
{
// if you got here, user had previously denied/revoked permission for your
// app to access the contacts, and all you can do is handle this gracefully,
// perhaps telling the user that they have to go to settings to grant access
// to contacts
[[[UIAlertView alloc] initWithTitle:nil message:#"This app requires access to your contacts to function properly. Please visit to the \"Privacy\" section in the iPhone Settings app." delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil] show];
block(nil);
}
CFErrorRef error = NULL;
ABAddressBookRef addressBook = ABAddressBookCreateWithOptions(NULL, &error);
if (error)
{
NSLog(#"ABAddressBookCreateWithOptions error: %#", CFBridgingRelease(error));
if (addressBook) CFRelease(addressBook);
block(nil);
}
if (status == kABAuthorizationStatusNotDetermined)
{
// present the user the UI that requests permission to contacts ...
ABAddressBookRequestAccessWithCompletion(addressBook, ^(bool granted, CFErrorRef error) -> THE ERROR OCCURS HERE !
{
NSString* result = whatever
block(result);
});
}
}
And use it like this:
[YourClass getAddressBook:^(NSString* result)
{
//now you really have result
}];