CODEWITHSUNDEEP
ioscore-datansmanagedobjectcontextnsoperationqueue
Stefan Arn
Stefan Arn

Reputation: 1154

How to cancel performBlock:

I implemented a search and for every new character typed by the user a performFetch: is started inside of a performBlock:. If the search string changes I would like to cancel the previous started block and start over. How would I cancel or at least inform the block inside the performBlock:about it?

Example code I have right now:

[myManagedObjectContext performBlock:^{
        // fetch from background queue
        if([[self fetchedResultsController] performFetch:nil]) {
            // update the view from the main queue
            // don't do this if performBlock already got started again! but how?
            [[NSOperationQueue mainQueue] addOperationWithBlock:^{
                // refresh UI
            }];
        }
    }];

Upvotes: 1

Views: 217

Answers (1)

Tom Harrington
Tom Harrington

Reputation: 70946

There is no API to cancel a performBlock. Once it starts, it continues until it completes or until your code returns from it.

If you find it necessary to cancel fetches while they are in progress, look into NSAsynchronousFetchRequest, which allows cancellation via NSProgress. Async fetch requests and cancellation are described in the WWDC 2014 Core Data session

Upvotes: 3

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