Unexplained `capturing self strongly` warning

Question

I have a number of methods in blocks, firing one inside the next, in order to sync some data with a web service. Most of these behave completely fine, but one method won't let me mention self after it's been called, giving me a capturing self strongly in this block is likely to lead to a retain cycle warning.

Here's what I mean:

[self deleteEntriesCorrespondingToDeletedNotesInNotebook:notebook success:^{
    [self deleteNotesToMatchDeletedEntriesWithCompletion:^{
       [self deleteResourcesToMatchDeletedMediaItemsWithCompletion:^{
           [self addOrUpdateEntriesCorrespondingToUpdatedNotesInNotebook:notebook success:^{
               //Anything calling a property or self after this point is a problem and gives the warning
               [self addOrUpdateNotesCorrespondingToUpdatedEntriesWithCompletion:^{

               }];
           }failure:^{

           }];
       }];
   }];
}failure:^{

}];

Any ideas why only items passed this point have a problem with this? If I replace the method before it with another similar method, there isn't a problem. The problem is only existent after addOrUpdateEntriesCorrespondingToUpdatedNotesInNotebook: is used.

Could you also add the internal implementations of each method? — Stavash, Jul 10 '13 at 09:43
Google "Objective-C blocks weak self", this is a dupe of lot of identical questions. — , Jul 10 '13 at 09:44
possible duplicate of [capturing self strongly in this block is likely to lead to a retain cycle](http://stackoverflow.com/questions/14556605/capturing-self-strongly-in-this-block-is-likely-to-lead-to-a-retain-cycle) — , Jul 10 '13 at 09:45
and of [How do I avoid capturing self in blocks when implementing an API?](http://stackoverflow.com/questions/7853915/how-do-i-avoid-capturing-self-in-blocks-when-implementing-an-api) — , Jul 10 '13 at 09:46
I know the ways to patch over the problem, using weak references, but I want to actually stop it from happening, since it doesn't happen with any other method. — Andrew, Jul 10 '13 at 09:49
If I understand it correctly, the question is **not** why this code generates a retain cycle, but why does `addOrUpdateEntries...` cause that warning, but `deleteEntries...` causes no warning. - I tried to answer that here: http://stackoverflow.com/a/15536473/1187415. — Martin R, Jul 10 '13 at 09:51
possible duplicate of [Clang - Blocks retain cycle from naming convention?](http://stackoverflow.com/questions/15535899/clang-blocks-retain-cycle-from-naming-convention) — rob mayoff, Jul 10 '13 at 09:57

score 3 · Answer 1 · answered Jul 10 '13 at 09:52

[self deleteEntriesCorrespondingToDeletedNotesInNotebook:notebook success:^{
    [self deleteNotesToMatchDeletedEntriesWithCompletion:^{  //this line here and the rest in your downward loop

dont use self. Instead do this before the first line

__typeof__(self) __weak _weakSelf = self; and then from second line onwards, replace self with weakSelf

try this. cheers

score 2 · Accepted Answer · edited May 23 '17 at 12:05

2

All of your methods could "behave fine" or create a retain cycle, depending on what they do with the completion block.

As explained here: Blocks retain cycle from naming convention?, the clang compiler uses naming conventions to decide whether to emit a warning or not: All methods add... and set... (but not addOperationWithBlock!) cause a warning, other methods don't.

edited May 23 '17 at 12:05

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answered Jul 10 '13 at 10:00

Martin R

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Unexplained `capturing self strongly` warning

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