Question

I have used NSMutable Dictionary and NSMutable Array. The datas are to be stored and retrieved from plist(Documents Directory) using NSArray of NSMutable Dictionary.

     Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[__NSCFArray removeObjectAtIndex:]: mutating method sent to immutable object' 

Please Guide me why its happened?.

Thanks!

Answer 1

It might help if you post the exact code that causes. My guess would be that while you are using NSMutableDictionary, the call to valueForKey: returns to you a non-mutable NSArray, and you think it is returning you an NSMutableArray instance. Note that mutable arrays and dictionaries allow you to manipulate the collection of items inside them, but do not guarantee you that those items themselves are mutable. For example, if you check the Property List Programming Guide: Reading and Writing Property-List Data, you will notice the following example:

If you load the property list with
this call:

NSMutableArray * ma = [NSMutableArray arrayWithContentsOfFile:xmlFile];

ma is a mutable array with immutable
dictionaries in each element. Each key
and each value in each dictionary are
immutable.

If you need explicit control over the mutability of the objects at each level, use propertyListFromData:mutabilityOption:format:errorDescription:

You can also create an explicit NSMutableArray copy from the NSArray you got from the NSMutableDictionary.