views:

11406

answers:

5

I'd like to save an NSMutableDictionary object in NSUserDefaults. The key type in NSMutableDictionary is NSString, the value type is NSArray, which contains a list of object which implements NSCoding. Per document, NSString and NSArray both are conform to NSCoding.

I am getting error :

-[NSUserDefaults setObject:forKey:]: Attempt to insert non-property value .... of class 'NSCFDictionary'.

Any solution for that?

Thanks.

+2  A: 

Are all of your keys in the dictionary NSStrings? I think they have to be in order to save the dictionary to a property list.

Ben Alpert
the keys are NSString. but the value is NSArray, whose element is a customized class which implements NSCoding. It appears that solution not working because UserDefaults only supports 6 types of class, not consider NSCoding.
BlueDolphin
+15  A: 

If you're saving an object in user defaults, all objects, recursively, all the way down, must be property list objects. Conforming to NSCoding doesn't mean anything here-- NSUserDefaults won't automatically encode them into NSData, you have to do that yourself. If your "list of object which implements NSCoding" means objects that are not property list objects, then you'll have to do something with them before saving to user defaults.

FYI the property list classes are NSDictionary, NSArray, NSString, NSDate, NSData, and NSNumber. You can write mutable subclasses (like NSMutableDictionary) to user preferences but the objects you read out will always be immutable.

Tom Harrington
I should also mention that an NSDictionary is only a property list object if the keys are NSStrings. In general you can use other objects as dictionary keys, but where property lists are required the keys must be strings.
Tom Harrington
+9  A: 

I found out one alternative, before save, I encode the root object (NSArray object) using NSKeyedArchiver, which ends with NSData. Then use UserDefaults save the NSData.

When I need the data, I read out the NSData, and use NSKeyedUnarchiver to convert NSData back to the object.

It is a little cumbersome, because i need to convert to/from NSData everytime, but it just works.

Here is one example per request:

Save:

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

NSMutableArray *arr = ... ; // set value

NSData *data = [NSKeyedArchiver archivedDataWithRootObject:arr];

[defaults setObject:data forKey:@"theKey"];

Load:

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

NSData *data = [defaults objectForKey:@"theKey"];

NSArray *arr = [NSKeyedUnarchiver unarchiveObjectWithData:data];

The element in the array implements

@interface CommentItem : NSObject {

NSString *value;

}

Then in the implementation of CommentItem, provides two methods:

-(void)encodeWithCoder:(NSCoder *)encoder

{

[encoder encodeObject:value forKey:@"Value"];

}

-(id)initWithCoder:(NSCoder *)decoder

{

self.value = [decoder decodeObjectForKey:@"Value"];

    return self;

}

Anyone has better solution?

Thanks everyone.

BlueDolphin
Do you have a code sample you can share, I've been trying to do this in post (537044) but with no joy
tigermain
This worked nicely for me. I was trying to encode an NSArray of NSDictionary objects where some of the keys were not strings. Simply using the NSKeyedArchiver and Unarchiver on the NSArray got rid of the "Attempt to insert non-property value" error.
John Wright
A: 

There is no better solution. Another option would be to just save the coded object to disk - but that is doing the same thing. They both end up with NSData that gets decoded when you want it back.

Dan Keen
+1  A: 

Have you considered looking at implementing the NSCoding Protocol? This will allow you encode and decode on the iPhone with two simple methods that are implemented with the NSCoding. First you would need to adding the NSCoding to your Class.

Here is an example:

This is in the .h file

@interface GameContent : NSObject <NSCoding>

Then you will need to implement two methods of the NSCoding Protocol.

    - (id) initWithCoder: (NSCoder *)coder
    {
        if (self = [super init])
        {
               [self setFoundHotSpots:[coder decodeObjectForKey:@"foundHotSpots"]];
            }
    }

    - (void) encodeWithCoder: (NSCoder *)coder
    {
           [coder encodeObject:foundHotSpots forKey:@"foundHotSpots"];
    }

Check out the documentation on NSCoder for more information. That has come in really handy for my projects where I need to save the state of the application on the iPhone if the application is closed and restore it back to it's state when its back on.

The key is to add the protocol to the interface and then implement the two methods that are part of NSCoding.

I hope this helps!

Niels Hansen