How can I prevent a scrollable UITableView from deallocating rows? - ios

Question

My problem's pretty simple.
I have a UITableViewController (well, I subclassed it, but that's not the issue), with a static layout, and it's large enough it doesn't fit on the screen all at one time.
I'm using viewWithTag to retrieve the values of a couple UISwitches, but they're just off the screen, so viewWithTag is infuriatingly returning nil.
Frankly, I neither know nor care about the memory overhead of leaving them in memory; it's not much memory to leave lying around, and I'm short on time.
How can I prevent scrolling from triggering deallocation?
EDIT: I know exactly what's wrong, as explained above, just not how to fix it (my usual google-fu came up dry). But since you asked to see the code...
int tag=200
int prefs = 0;
for (int i=0; i != 3; ++i) // There are only 3 preferences
{
prefs = prefs << 1;
UISwitch *swt = (UISwitch *)[self.view viewWithTag:tag + i];
NSLog(#"%#", swt);
if ([swt isOn])
++prefs;
NSLog(#"%d", prefs);
}
The above code works in viewDidAppear (because the switches are at the top of the table), but not once I have scrolled to the bottom of the table (viewWithTag returns null).

Answer 1

All objects of your cells are available and not destroyed whether on or off the screen. TableView simply reuses the cell.
Hence, you can get any cell's object by:
UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:<requiredIndexPath>];
// Check the status of your cell's switch.
Loop through all the cells of the tableView and you will get it
Take a look at the documentation by Apple

Answer 2

If you are using UITableView, then this is absolutely not how it works.
For a UITableView, implement numberOfRowsInSection and cellForRowAtPathIndex, and when you want to change one of the cells, call reloadRowsAtIndexPath.

Answer 3

If you want to access the switch, you should access the object you pass to the data source. There you can access the switch value.
I think you are trying to make a setting in tableView. Here on what I usually do
// create an array to hold the setting data
NSArray *settingArray = #[#{#"title":#"Frequently Asked Questions"},#{#"title":#"Need Help?"},#{#"title":#"Push Notification",#"hasSwitch":[NSNumber numberWithBool: YES],#"switchValue":[[NSUserDefaults standardUserDefaults]boolForKey:#"kPushPreference"]}];
// data source
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return self.settingsArray.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
SettingCell *cell = [tableView dequeueReusableCellWithIdentifier:#"SettingCell" forIndexPath:indexPath];
NSDictionary *dictionary = self.settingsArray[indexPath.row];
[cell.settingName setText:dictionary[#"title"]];
if (dictionary[#"hasSwitch"]) {
[cell.settingSwitch setHidden:NO];
[cell.settingSwitch setOn:dictionary[#"switchValue"]];
}
return cell;
}
`