To create action of the text field to populate a label...
- (IBAction) sgDoneEditing:(id) sender
{
UITextField *textField = (UITextField *)sender;
NSString *textFieldValue = textField.text;
NSString *label = [[NSString alloc] initWithFormat:@"S.G.: %@", textFieldValue];
sgValue.text = label;
[label release];
}