Observe the changes of a property of objects in a mutable array

Question

I have a table view of objects Object in an array _objects. Each object has a property status that I want to display in the table view.

My question is, how can I do this using KVO ?

I need to observe addition/removal, I think I got that working with KVO on the array itself, but I also need to observe each object's status keypath to update the table view cell.

Answer 1

Subclass UITableViewCell, add a property "object" and add an observer for the keypath "object.status" in the initializer or viewDidLoad of your table view cell. In "cellForRowAtIndexPath:" you'll dequeue / create the cell and set the object property.

Answer 2

I think you are looking for willChangeValueForKey and didChangeValueForKey methods used in KVO.

Here is a pretty good writeup this guy used to understand the same concept: http://horseshoe7.wordpress.com/2013/01/28/kvo-observing-any-change-in-object-state/

Here are some others:

http://www.andyibanez.com/74-key-value-coding-key-value-observing-and-cocoa-bindings-a-basic-tutorial

Key-Value Observing with NSMutableData iOS