Question

I have a UITableViewController and in the didSelectRowAtIndexPath method I create an instance of a UIViewController and push it on to the stack.

The UIViewController is meant to edit the content of the selected cell but how do I get the changes made in the ViewController transfered back to the TableViewController?

Cheers

Answer 1

The standard way to pass data back up the hierarchy is with delegation or even more simply through querying a property on the edit view controller when you want to get the edited data back.

Now, when it comes to edit view controllers you can design them to support both direct editing of ‘live’ objects, or a copy which will let you do a Save/Cancel model.

So what you want is for your edit view controller to edit some sort of ModelObject instance with various properties. These properties will correspond to the textfields or date-pickers etc. in the view. So you might have a Person with NSDate *dateOfBirth and NSString *name.

When you create the view controller and push it onto the navigation controller, you give it one of these ModelObjects to edit. You can either pass in an object straight from your model which will be edited ‘live’ as the user enters values, or a copy which will let you discard changes and implement a Save or Cancel workflow. For the latter you can add the Save and Cancel buttons yourself before you push the edit view which lets you handle the actions yourself without needing delegation.

So your edit view controller will set the properties on this object when the user enters a new value in a textfield or changes the date picker. For a live object these changes will be applied immediately to your model. For a copy, when the user hits Save you query the edit view controller for the object you passed in and merge/copy that back into your model. If the user hits cancel, you just discard the object.