How to assign copy of object back to original reference?

Question

I have application with following design: Table View that lists documents. And ViewController where document is edited.

When editing the document I want to use a copy of object so in case user press Cancel I just throw away the copy. If user selected Save I copy modified document to original. (I can't have all document's fields as properties in viewController because there are too many of them).

Table View controller:

SelectedRowAtIndex {
  document= [documentsArray objectAtIndex:indexPath.row];
  viewController.assignedDocuemnt= document;
}

Then I have View controller class where the item is modified:

@interface
@property (nonatomic,retain) Document *asignedDocument;
@property (nonatomic,retain) Document *editedDocument;

viewDidLoad{
   editedDocument= [assignedDocuemnt copy];
}


IBAction save {
   assignedDocument=editedDocument;
}

My problem is that original document in documentsArray is not updated with edited version. What did I miss?

Answer 1

You're copying the value and then assigning the reference of the copy back over a reference to the original. That's definitely not going to work.

First, keep track of which document they're adding in the table view's viewcontroller.

Then add a handler for replacing the selected document with another to the table view's viewcontroller:

- (void)replaceSelectedDocument:(Document*)newDoc {
    [documents replaceObjectAtIndex: editingIndex
                         withObject: newDoc];
}

To save, call the table view controller's new message from the editor view controller with something like:

[tableViewController replaceSelectedDocument: editedDocument];

A better way to do this would be to modify your editor view controller to take a target and action instead of calling back to the table view controller explicitly. When you want to save, call the action:

[target performSelector: action withObject: editedDocument];

But that's another bump on the learning curve that you probably don't need to get over today.