xcode objective-c GCD dispatch group wait example

xcode objective-c GCD dispatch group wait example

//first

dispatch_async(queue, ^{

    dispatch_group_t group1 = dispatch_group_create();


    //   Tasks goes here

    for (NSInteger i = 0; i < 3; i++) {

        dispatch_group_enter(group1);

        someTaskWithCompletitionBlock:^() {
            dispatch_group_leave(group1);
        };
    }

    dispatch_group_wait(group1, DISPATCH_TIME_FOREVER);

    dispatch_async(dispatch_get_main_queue(), ^{
        // Perform completition block
    });

});

//second

dispatch_group_t group2 = dispatch_group_create();

for (NSInteger i = 0; i < 3; i++) {
    
    dispatch_group_enter(group2);
    
    someTaskWithCompletitionBlock:^() {
        dispatch_group_leave(group2);
    };
    
}

dispatch_group_notify(group2, dispatch_get_main_queue(), ^{
    // Perform completition block
});