Master-Detail Application with Core Data

Question

From Xcode 4.2 Master-Detail template (for iPad) with Core Data, I modified the data model and added additional text view objects to the nib file.

Code for moving data from managed object to interface objects is in ConfigureView in DetailViewController and it's working fine.

I'm now trying to auto save the interface object data to managed object data when I move from one item to another in the popover.

I added the code for save in viewWillDisappear in DetailViewController, but this doesn't seem to fire. Am I missing something?

- (void)configureView { // Update the user interface for the detail item.
  if (self.detailItem) {
    self.sname.text = [self.detailItem valueForKey:@"sname"];
    self.saddress.text = [self.detailItem valueForKey:@"saddress"];
  }
}


- (void)viewWillDisappear:(BOOL)animated {
  [self.detailItem setValue: self.sname.text forKey:@"sname"];
  [self.detailItem setValue: self.saddress.text forKey:@"saddress"];

  NSError *error; if (![self.detailItem.managedObjectContext save:&error]) {
    NSLog(@"Unresolved error %@, %@",error,[error userInfo]);
    exit(-1); //fail
  }

  [super viewWillDisappear:animated];
}

- (void)configureView { // Update the user interface for the detail item. if (self.detailItem) { self.sname.text = [self.detailItem valueForKey:@"sname"]; self.saddress.text = [self.detailItem valueForKey:@"saddress"]; } } — Rams, Jan 08 '12 at 16:59
- (void)viewWillDisappear:(BOOL)animated { [self.detailItem setValue: self.sname.text forKey:@"sname"]; [self.detailItem setValue: self.saddress.text forKey:@"saddress"]; NSError *error; if (![self.detailItem.managedObjectContext save:&error]){ NSLog(@"Unresolved error %@, %@",error,[error userInfo]); exit(-1); //fail } [super viewWillDisappear:animated]; } — Rams, Jan 08 '12 at 17:02
Please put the code as an edit to your question, not as comments. — jrturton, Jan 08 '12 at 17:08

timthetoolman · Answer 1 · 2012-01-08T17:08:59.633

First, in a MasterDetail application the detailViewController is usually always be visible and not disappear. So that is why viewWillDisappear is not being called. Of course I'm not sure about the particulars of your app architecture, so I may be wrong.

Secondly, consider the use case if the user changes some data then switches to another application. Then while in the other application, the system terminates your app. The changes that your user made will be lost and will run counter to what they expect.

Unless you are saving a lot of data for the interface in detailViewController, consider saving the data after the user changes data in the interface rather than when the user switches from managedObject to managedObject in the popoverViewController. i.e. when the user edits some data in a textView or textfield, perform a save on the managedObjectContext.

Good Luck!

Master-Detail Application with Core Data

1 Answers1