Calling UITableView datasource methods beforehand when the view is not present - ios

Question

I have dropped my code into a situation where I need to call UITableView data source methods written in some UIViewController class before a particular view is presented so that the cells get prepopulated and I can set a BOOL that the data in the not present viewController class is valid or not. I may explain it in more detail if required, but I wanted to know if its possible to do that. If yes, then how to do it? .. as a particular set of my code written after [tableView reloadData] is dependent on running the dataSource methods of UITableView. Please throw some light on this, if needs to be handled in a specific thread?
Following is the case where I call reloadData. Note: This is happening in another class when basicFactsViewController's viewWillAppear method has not been called yet:
- (BOOL) isComplete {
dispatch_async(dispatch_get_main_queue(), ^{
[basicFactsViewController.tableView reloadData];
});
return basicFactsViewController.isComplete && selectedVehicleId && selectedMakeId && selectedModelId && selectedYearId && selectedTrimId;
}
Now basicFactsViewController.isComplete is checked in this method:
- (BOOL) isComplete {
[self collectKeyHighlights];
return _isComplete;
}
Now the dictionary "tableCells" in the method below uses the cells population to check whether all features have been completed or not:
- (NSDictionary *) collectKeyHighlights {
NSMutableDictionary *key_highlights_update = [NSMutableDictionary new];
NSMutableDictionary *cell_highlight_update = [NSMutableDictionary new];
if(visible_key_highlights.count == 0) _isComplete = YES;
_isComplete = YES;
__block NSMutableArray *reloadCellAtIndexPathSet = [[NSMutableArray alloc] init];
[visible_key_highlights enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSDictionary *feature = (NSDictionary *)obj;
UITableViewCell *cell = [self.tableCells objectForKey:[NSIndexPath indexPathForRow:idx inSection:0]];
if(cell) {
if([cell isKindOfClass:[DRColorSelectionTableViewCell class]]) {
NSInteger selectedIndex = ((DRColorSelectionTableViewCell *)cell).selectedIndex;
NSInteger numberOfSegments = ((DRColorSelectionTableViewCell *)cell).numberOfSegments;
if(selectedIndex > -1 ) {
NSArray *dataValues = [[visible_key_highlights objectAtIndex:idx] objectForKey:#"data_values"];
NSDictionary *colorData;
BOOL reloadCellForIndexPath = NO;
if (numberOfSegments == selectedIndex) {
colorData = #{ #"normalized" : #"user_defined", #"isother" : #YES, #"hexcode":#"#FFFFFF", #"actual":((DRColorSelectionTableViewCell *)cell).otherColorTextField.text};
reloadCellForIndexPath = YES;
}
else{
colorData = [dataValues objectAtIndex:selectedIndex];
}
[key_highlights_update setObject:colorData forKey:[feature objectForKey:#"name"]];
[cell_highlight_update setObject:colorData forKey:[feature objectForKey:#"name"]];
if (![colorData isEqual:[prevSelections objectForKey:[feature objectForKey:#"name"]]]) {
[reloadCellAtIndexPathSet addObject:((DRColorSelectionTableViewCell *)cell).indexPath];
}
//if (reloadCellForIndexPath) {
//}
} else {
_isComplete = NO;
}
} else if([cell isKindOfClass:[DRInputTableViewCell class]]) {
NSString *textInput = ((DRInputTableViewCell *)cell).inputTextField.text;
if([textInput length]) {
[key_highlights_update setObject:[NSString toSnakeCase:textInput] forKey:[feature objectForKey:#"name"]];
[cell_highlight_update setObject:textInput forKey:[feature objectForKey:#"name"]];
}else {
_isComplete = NO;
}
} else if([cell isKindOfClass:[DRPickerTableViewCell class]]) {
NSString *textInput = ((DRPickerTableViewCell *)cell).inputField.text;
if([textInput length]) {
[key_highlights_update setObject:[NSString toSnakeCase:textInput] forKey:[feature objectForKey:#"name"]];
[cell_highlight_update setObject:textInput forKey:[feature objectForKey:#"name"]];
} else {
_isComplete = NO;
}
} else if([cell isKindOfClass:[DRSwitchTableViewCell class]]) {
// send this everytime for now
BOOL isSelected = ((DRSwitchTableViewCell *)cell).toggleButton.selected;
[key_highlights_update setObject:[NSNumber numberWithBool:isSelected] forKey:[feature objectForKey:#"name"]];
[cell_highlight_update setObject:[NSNumber numberWithBool:isSelected] forKey:[feature objectForKey:#"name"]];
}
}
else{
_isComplete = NO;
}
}];
prevSelections = cell_highlight_update;
if ([reloadCellAtIndexPathSet count]) {
[self.tableView beginUpdates];
[self.tableView reloadRowsAtIndexPaths:reloadCellAtIndexPathSet withRowAnimation:UITableViewRowAnimationNone];
[self.tableView endUpdates];
}
return key_highlights_update;
}
Now here since
[tableView reloadData]
is not calling cellForRowAtIndePath:, hence, tableCells is not getting populated, hence, I am always getting _isComplete = NO.

Answer 1

If I understand correctly, there is processing being done when the tableview loads (calls it's dataSource methods) and you want to trigger that early to use its results. Calling [basicFactsViewController.tableView reloadData]; early won't work if the basicFactsViewController hasn't been displayed yet. If basicFactsViewController is a UIViewController and has the default view and the tableView property is a subview of that standard view, then (if I remember correctly) the tableView property will be nil until the basicFactsViewController has been displayed. A shortcut around that is to access the viewController's view property and cause it to initialize (viewDidLoad and all that). You can do that by simply messaging the viewController: [basicFactsViewController view].
If I've been right so far I'm fairly confident that will initialize the tableView property. But I'm not sure if it will cause the table view to load its data. And even if it does work, it's definitely not the best solution to the piece of code you're trying to architect. Apple's design for UIKit has been focused on the model/view/controller pattern and it's easier to go with the flow and do the same. I imagine that you could move the processing that is in the data source methods for the tableView out into another class (or maybe even the same class), and call that method to get everything ready for both the tableView and any other checks that you have, storing the data in dictionaries and arrays in such a way that you can easily load them by index into the tableView when cellForIndex is called.