Question

I’m develop app for iPhone & iPod and during developing app i used simulator 3.2(iPad) it runs perfectly but when I want to my app on simulator 3.1.3 it generate one error I remove this error by comment this line //self.clearsSelectionOnViewWillAppear = NO;
and build project successfully but run app on simulator 3.1.3 when i clicking on button it goes on another screen on 3.2 simulator perfectly & crash on 3.1.3
what i do for come out from it.

Answer 1

The docs for UITableViewController clearly state that clearsSelectionOnViewWillAppear is available on iOS 3.2 and above. It crashes in 3.1.3 because this property does not exist in 3.1.3 (you can easily surmise this from reading the documentation for the property that you have already discovered is causing the issue, or from looking at the error message which will indicate that the object does not respond to a selector for setClearsSelectionOnViewWillAppear.

Before setting this, you can check for this property and then set it, otherwise your older code can just be supported as is, or you could do something more advanced and add the property in pre-3.2 environments.

To check for the code, you do something like this:

if( [UITableViewController instancesRespondToSelector:@selector(setClearsSelectionOnViewWillAppear:)] ) {
  // This is 3.2+ so we can use this property
  [self setClearsSelectionOnViewWillAppear:NO];
} else {
  // This is something earlier than 3.2, so we ignore it
  NSLog(@"will clear selection: pre-3.2");
}