Asynchronous loading of data from multiple api - ios

Question

Loading data from one api request and storing it in one array (suppose n object coming in response json object),
and another api request takes argument from first api request and loads status of n objects.
1) first api request will load n objects and display it into table:
dispatch_queue_t loadDataQueue = dispatch_queue_create("loadDataQueue",NULL);
dispatch_async(loadDataQueue, ^{
// Perform long running process
[self loadData];
dispatch_async(dispatch_get_main_queue(), ^{
// Update the UI
[tableView reloadData];
[self hideActivityView];
});
});
2) now I am calling loadstatus method, it takes parameter from objectatindex and loads status data for objectatindex. So this method calling n times in cellForRowAtIndexPath method.
dispatch_queue_t loadStatusQueue = dispatch_queue_create("loadStatusQueue",NULL);
dispatch_async(loadStatusQueue, ^{
// Perform long running process
[self loadStatus];
dispatch_async(dispatch_get_main_queue(), ^
// Update the UI
[tableView reloadData];
});
});
This updates one row at a time. So reloading table n times.
It takes so time to load status of all objects.
Some time hanging problem occured.
Can somebody please provide efficient solution for this or other way to do this?

Answer 1

The info in your question was a bit unclear ( especially about objectAtIndex... Does it mean that in cellForRowAtIndexPath you get the cell's info, then based on that you send another async request to get it's status?)
It might not be enough to tell all reasons could make your app slow, but I could say it's not a good idea to reload the whole table just to update one cell. Also I think you should call loadData to get full data list of basic info first, then call loadStatus for 'visible' cells.
I guess you know how to store the loaded data/status in arrays to prevent refetching data. So the example below is possibly what you could adopt to improve the performance:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier:#"ReusableCell" forIndexPath:indexPath];
[cell configureData:self.loadedData[indexPath.row]];
if (self.loadedStatus[indexPath.row]) {
// If the status has been loaded then
[cell configureStatus:self.loadedStatus[indexPath.row]];
} else {
dispatch_queue_t loadStatusQueue = dispatch_queue_create("loadStatusQueue",NULL);
__weak __typeof(self) weakSelf = self;
dispatch_async(loadStatusQueue, ^{
__strong __typeof(weakSelf) strongSelf = weakSelf;
if (!strongSelf) {
return;
}
// Perform your long running process here
// Eg: [strongSelf loadStatusForIndex:indexPath.row];
UITableViewCell *blockCell = (UITableViewCell *)[strongSelf.tableView cellForRowAtIndexPath:indexPath];
dispatch_async(dispatch_get_main_queue(), ^{
[strongSelf.tableView reloadRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationNone];
});
}
});
....
}
return cell;
}