On Nov 30, 2008, at 3:35 PM, Alexander Cohen wrote:
Hi, Im getting the following line in the console when sending the
'removeObjectsAtArrangedObjectIndexes:' message to an
NSArrayController instance.
-[NSCFArray removeObjectAtIndex:]: mutating method sent to immutable
object
I understand what it means but i'm not sure why it's happening. Is
there anything i need to set up in order for the contents of the
arrayController to be mutable?
The array controller is bound to a to-many property of some other
object. That to-many property is not properly mutable.
You may be tempted to change that property's type from NSArray to an
NSMutableArray, but that's not the right solution. The right solution
is to implement the mutating indexed accessors for the property:
The minimal accessors for read access:
-countOf<Key>
-objectIn<Key>AtIndex:
One (or both) of the insertion methods:
-insertObject:in<Key>AtIndex:
-insert<Key>:atIndexes:
One (or both) of the removal methods:
-removeObjectFrom<Key>AtIndex:
-remove<Key>AtIndexes:
Optionally, for performance:
-get<Key>:range:
-replaceObjectIn<Key>AtIndex:withObject:
(Note, you can use an NSMutableArray as the backing store for the
property, but that's different and separate from changing the type of
the property to NSMutableArray. The latter violates encapsulation by
allowing code outside of your class to modify the state of your
objects without them being aware of it.)
Cheers,
Ken
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