Completion Block called twice

[jeremyquinn]

I have classes extending Operation, that add a completionBlock to self during init, to run a custom completionBlock.
The completionBlock is running twice.
There was a similar problem with Dan Thorpe's Operations GitHub project, it looks very similar : ProcedureKit/ProcedureKit#123

[mcmurrym]

I think the fix should be not allowing completionBlock property to operate at all within PSOperations. We have seen this issue, we have also seen weird time of the execution of the block which makes the state of the operation in the completionBlock inconsistent (regardless of PSOperations). I believe @davedelong has even filed a radar to have this property deprecated. If you want to execute code at the end of an operation try the Observer class, you can easily do it with BlockObserver and it will always execute at the expected time.

That said, we are always open to pull requests for the fix.

[davedelong]

I'd totally be in favor of seeing this property marked as unavailable. And yes, I did file that bug: rdar://problem/23915499 Deprecate completionBlock

[jeremyquinn]

Hi Guys
Thanks for this.
Yes, I worked around the problem by performing the custom completion block either in a defer clause in Operation.execute or in the case of a GroupOperation, wrapped in a BlockOperation, with the correct dependencies to run last.
This is such a great framework, thanks for all of your work!!

[mcmurrym]

We have now deprecated the completionBlock property within PSOperations.