I have an NSOutlineView bound to an NSTreeController. My data items are a custom class, let's call them Row, and suppose a Row contains a name and a numeric field called number.
All these Rows are found in let's say a RowContainer which has a rows mutable array holding the parent (level 0) rows. Each row also has a children NSMutableArray member which holds its children.
I have this working, and I want to display under the outline view a text field with the sum of all the number values of the rows.
I bound this text field to a total property of the RowContainer. Now the problem is how or from where to trigger the recalculation of the total property, since this involves a recursive walk on the tree of rows, and I always get a Collection was mutated while being enumerated error.
I've tried making a method recalculateTotal, and calling it from the setNumber method of the Row class , but same error occurs. If I put the recalculation logic in the total getter, I can't trigger it to do the math.
I'm sure the solution is simple but I can't see it.