CODEWITHSUNDEEP
iosobjective-cuicollectionviewpull-to-refresh
user2823044
user2823044

Reputation: 315

pull to refresh crashes ios app

I'm using pull to refresh in my app for collection view but app is crashing with error.

*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 2 beyond bounds for empty array'

I'm using asynchronous queue to get the data from server.

Following is my code to get the data from server and update ui on success:

     refreshControl = [[UIRefreshControl alloc] init];
     [refreshControl addTarget:self action:@selector(startRefresh:)
           forControlEvents:UIControlEventValueChanged];

- (void)startRefresh:(UIRefreshControl *)refreshcontrol
{
    dispatch_queue_t fetchQueue = dispatch_queue_create("fetch Queue", NULL);

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
     //webservice call which on success post notification
    });
}


- (void)onSuccess:(NSNotification *)success { //notification after success of webservice
    [storyCollectionView setHidden:NO];
    NSLog(@"fun:%s", __func__);

    dispatch_async(dispatch_get_main_queue(), ^{//in the main queue i'm ending refresing
        if ([refreshControl isRefreshing]) {
        [refreshControl endRefreshing];
        } 

    [CollectionView reloadData];// reloading collection view
    }
                   );

  }

Upvotes: 0

Views: 1204

Answers (5)

HardikDabhi
HardikDabhi

Reputation: 2952

I think you should reload your collection view or tableview after calling refreshcontrol.endrefreshing. Like:-

@objc func refresh(sender:AnyObject) {
        // Code to refresh table view
        //Do all other API Calling stuff here
        refreshControl.endRefreshing()
        self.tableviewList?.reloadData()
    }

It will work perfectly!! :)

Upvotes: 3

Mahesh reddy
Mahesh reddy

Reputation: 134

The problem is your taking the values from array without checking the size of array

Upvotes: 0

jenish
jenish

Reputation: 268

when performing pull to refresh . its default behaviour to reload table at that time your array becomes blank so it will be crash. so for this alloc your array after getting web service response. 

dispatch_queue_t fetchQueue = dispatch_queue_create("fetch Queue", NULL);

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
 //webservice call which on success post notification
});

there is no required to use this methodall time . it reduce app performance. because it waiting for Queue or main thread becomes free.

Upvotes: 0

karthik
karthik

Reputation: 1281

In your collection view datasource check if the array is empty , you are trying to access an empty array, use below code to check array is empty and return 0.

if (array == nil){
   return 0;
}

Upvotes: 0

Yong Li
Yong Li

Reputation: 266

That's because the data in your data model is inconsistent with with the UITableView's date source methods returns.

Upvotes: 1

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