NSManagedObject hierarchy import and export

Question

I'm on the run to make my NSMangedObjectClass profile im-/exportable.
I try it this way
Exporting works correctly if I write the Relationships in NSArrays because NSSet doesn't have writeToFile implemented.

- (void) exportProfile:(Profile *)profile toPath:(NSString *)path{
//Profile
NSMutableDictionary *profileDict = [[self.selectedProfile dictionaryWithValuesForKeys:[[[self.selectedProfile entity] attributesByName] allKeys]] mutableCopy];
NSMutableArray *views = [NSMutableArray array];

//Views
for (View *view in selectedProfile.views) {
    NSMutableDictionary *viewDict = [[view dictionaryWithValuesForKeys:[[[view entity] attributesByName] allKeys]] mutableCopy];
    NSMutableArray *controls = [NSMutableArray array];
         //Much more for-loops
    [viewDict setObject:controls forKey:@"controls"];
    [views addObject:viewDict];
}

[profileDict setObject:views forKey:@"views"];

if([profileDict writeToFile:[path stringByStandardizingPath] atomically:YES]) 
    NSLog(@"Saved");
else
    NSLog(@"Not saved");
[profileDict release];
}

But if want to import on the other side

- (Profile*) importProfileFromPath:(NSString *)path{
NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
Profile *newProfile = [NSEntityDescription insertNewObjectForEntityForName:@"Profile" inManagedObjectContext:context];

NSMutableDictionary *profileDict = [NSMutableDictionary dictionaryWithContentsOfFile:[path stringByStandardizingPath]];
[newProfile setValuesForKeysWithDictionary:profileDict];
}

I get an exception, this doesn't confuse me cause Profile expects a NSSet and no NSArray.
[__NSCFArray intersectsSet:]: unrecognized selector sent to instance 0x4e704c0 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFArray intersectsSet:]: unrecognized selector sent to instance 0x4e704c0'
So I've got two problems:

On the one side, I can't write a NSSet to File.
On the other side is my Profile class expecting an NSSet.

So I tried to create a Category of NSSet which implements writeToFile

@implementation NSSet(Persistence)

- (BOOL)writeToFile:(NSString*)path atomically:(BOOL)flag{
    NSMutableArray *temp = [NSMutableArray arrayWithCapacity:self.count];
    for(id element in self)
        [temp addObject:element];
    return [temp writeToFile:path atomically:flag];
}

+ (id)setWithContentsOfFile:(NSString *)aPath{
    return [NSSet setWithArray:[NSArray arrayWithContentsOfFile:aPath]];
}
@end

But my functions aren't called.

Is there a other way to write my NSSet or tell setValuesForKeysWithDictionary the Key "views" is a NSArray?

Or a easy Way to im-/export ManagedObjects?

`NSSet` has an instance method `- (NSArray *)allObjects` and a class method `+ (id)setWithArray:(NSArray *)array` which may help you. — Joe, Apr 11 '11 at 15:22
`[__NSCFArray intersectsSet:]: unrecognized selector sent to instance 0x4e704c0 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFArray intersectsSet:]: unrecognized selector sent to instance 0x4e704c0'` like i said Profile expects a NSSet and calls functions of NSSet and not the NSArray methods — Seega, Apr 11 '11 at 15:23
+1: might want to add the exception in to your question so its easier to spot. otherwise, gl on the problem! — Jesse Naugher, Apr 11 '11 at 15:31

Seega · Accepted Answer · 2011-04-12T10:19:35.187

Got problems with the nested NSDictonarys, so i said goodbye to the dynamic way. Here is my complete Solution to help others
ViewController to call the im/export functions

- (void) exportProfile:(Profile *)profile toPath:(NSString *)path{
    //Call the NSManagedobject function to export
    NSDictionary *profileDict = [self.selectedProfile dictionaryForExport];

    if([profileDict writeToFile:[path stringByStandardizingPath] atomically:YES]) 
        NSLog(@"Saved");
    else
        NSLog(@"Not saved");
}

- (void) importProfileFromPath:(NSString *)path{
    NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
    Profile *newProfile = [NSEntityDescription insertNewObjectForEntityForName:@"Profile" inManagedObjectContext:context];

    //load dictonary from file
    NSMutableDictionary *profileDict = [NSMutableDictionary dictionaryWithContentsOfFile:[path stringByStandardizingPath]];
    //call the NSManagedObjects import function
    [newProfile importWithDictonary:profileDict context:context];

    NSError *error = nil;
    if (![context save:&error]) {

        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
}

NSManagedObject functions i got a hierarchy so i put them in each of my NSManagedObjects

- (void) importWithDictonary:(NSDictionary*)dict context:(NSManagedObjectContext*)context{
    self.name = [dict objectForKey:@"name"];

    //Relationship
    for (NSDictionary *view in [dict objectForKey:@"views"]) {
        View *tempView = [NSEntityDescription insertNewObjectForEntityForName:@"View" inManagedObjectContext:context];
        [tempView importWithDictonary:view context:context];
        tempView.profile = self;
        [self addViewsObject:tempView];
    }
}

- (NSDictionary*) dictionaryForExport{ 
    //propertys
    NSMutableDictionary *dict = [[[self dictionaryWithValuesForKeys:[[[self entity] attributesByName] allKeys]] mutableCopy] autorelease];
    NSURL *objectID = [[self objectID] URIRepresentation];
    [dict setObject: [objectID absoluteString] forKey:@"objectID"];
    NSMutableArray *views = [NSMutableArray array];

    //relationship
    for (View *view in self.views) {
        [views addObject:[view dictionaryForExport]];
    }
    [dict setObject:views forKey:@"views"];
    return dict;
}

not the most beautiful solution but it works :)
and i have still to figure out how to avoid duplicates in my n:m relationship

Thanks

Any particular use of this statement while exporting the dictionary? - NSURL *objectID = [[self objectID] URIRepresentation]; — Raj Pawan Gumdal, Jul 09 '12 at 18:52

score 1 · Answer 2 · answered Apr 11 '11 at 15:57

1

You could try overriding NSManagedObject's default implementation of setValuesForKeysWithDictionary ?

Looking at the documentation you should only have to implement setValue:forKey: in your subclasses?

You should be able grab the NSSet in there and deal with it yourself before the exception gets thrown?

[Disclaimer - I have never done this!]

answered Apr 11 '11 at 15:57

deanWombourne

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thanks, thought about this on my way home, will try it tomorrow. – Seega Apr 11 '11 at 18:41

NSManagedObject hierarchy import and export

2 Answers2