Multiple calculateDirectionsWithCompletionHandler with GCD in iOS App

Asked Apr 01 '14 at 12:46

Active Apr 01 '14 at 13:48

Viewed 438 times

I need to do multiple request for a MKDirections (10) and I want to make faster my iOS7 App. After 10 calculateDirectionsWithCompletionHandler, I want to update user interface. I try with async calls with GCD.

My problem is that with GCD I don't understand how to wait the end of all calculateDirectionsWithCompletionHandler before to update user interface.

This is my code:

dispatch_group_t taskGroup =  dispatch_group_create();
dispatch_queue_t mainQueue =  dispatch_get_main_queue();

dispatch_group_async(taskGroup, mainQueue, ^{
    [directions1 calculateDirectionsWithCompletionHandler:
     ^(MKDirectionsResponse *response, NSError *error) {...}];
});

.........

dispatch_group_async(taskGroup, mainQueue, ^{
    [directions10 calculateDirectionsWithCompletionHandler:
     ^(MKDirectionsResponse *response, NSError *error) {...}];
});

/* Update UI */
dispatch_group_notify(taskGroup, mainQueue, ^{

    /* Do some processing here and UI Update */

});

The problem is that the UI is updated before of the end of all calculateDirectionsWithCompletionHandler!

Why? Which is the problem in my code?

Thank you for help.

edited Apr 01 '14 at 13:48

Mehmet Emre Portakal

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asked Apr 01 '14 at 12:46

katundo

You can refer the link http://stackoverflow.com/questions/11909629/waiting-until-two-async-blocks-are-executed-before-starting-another-block – user2071152 Apr 01 '14 at 13:05
Please can you explain to me? I don't understand. – katundo Apr 01 '14 at 13:06
At a simple level you could keep an int reference to the number of updates received, and then fire your update method once it reaches 10 ? – GuybrushThreepwood Apr 01 '14 at 13:57
Please can you give me an example? – katundo Apr 01 '14 at 15:22

Multiple calculateDirectionsWithCompletionHandler with GCD in iOS App

0 Answers0