CODEWITHSUNDEEP
iosjsonsqlitecore-data
user2512523
user2512523

Reputation: 1359

JSON to Core Data SQLITE Error

Can anyone help figure out what i've done wrong within this code? trying to populate core data structure through JSON file

// Create the managed object context
    NSManagedObjectContext *context = managedObjectContext();
    // Save the managed object context
    NSError *error = nil;
    if (![context save:&error]) {
        NSLog(@"Error while saving %@", ([error localizedDescription] != nil) ? [error localizedDescription] : @"Unknown Error");
        exit(1);
    }

    NSError* err = nil;
    NSString* dataPath = [[NSBundle mainBundle] pathForResource:@"Exercises" ofType:@"json"];
    NSArray* Exercises = [NSJSONSerialization JSONObjectWithData:[NSData dataWithContentsOfFile:dataPath]
                                                         options:kNilOptions
                                                          error:&err];
    //NSLog(@"Imported Exercises: %@", Exercises);
    NSManagedObject *object = [NSEntityDescription insertNewObjectForEntityForName:@"Exercise" inManagedObjectContext:context];
    NSString *theJSONString = @"{\"key\":\"value\"}";
    NSError *theError = NULL;
    NSDictionary *jsonDict = [NSDictionary dictionaryWithJSONString:theJSONString error:&theError];

    Exercise *exercise = [NSEntityDescription insertNewObjectForEntityForName:@"Exercise"
                                                       inManagedObjectContext:context];

    [Exercises enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

        NSDictionary *attributes = [[object entity] attributesByName];
        for (NSString *attribute in attributes) {
            id value = [jsonDict objectForKey:attribute];
            if (value == nil) {
                continue;
            }
            [exercise setValue:value forKey:attribute];
        }
        NSError *error;
        if (![context save:&error]) {
            NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
        }
    }];

Edited: Code now compiles but i get null values in the core data model. Thanks

Upvotes: 0

Views: 248

Answers (1)

Tom Harrington
Tom Harrington

Reputation: 70976

First, this isn't a SQLite error, it's a standard, basic Objective-C error. You'd have the same problem even if you weren't using a SQLite-based Core Data store.

Let's work backward from where it looks like the error is occurring, which is:

NSDictionary *attributes = [[obj entity] attributesByName];

You're calling entity on obj. But where did obj come from? From here:

[Exercises enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

OK, so obj came from Exercises. What is in Exercises?

NSArray* Exercises = [NSJSONSerialization
    JSONObjectWithData:[NSData dataWithContentsOfFile:dataPath]
    options:kNilOptions
    error:&err];

Exercises is an array of things that NSJSONSerialization gave you. The JSONObjectWithData:options:error: method gives you Cocoa equivalents for the JSON content. It does not give you managed objects. In this case it looks like your JSON produced an array of NSDictionary.

So what happened is:

  1. You used NSJSONSerialization and got an array of dictionaries
  2. You iterated over that array
  3. You attempted to call entity on the members of the array, only the array members are NSDictionary instances, and that class does not implement entity.

Your code never creates any Core Data objects, anywhere. That's why you're not getting any Core Data objects. Your code is crashing because you're trying to call Core Data methods on objects that don't implement those methods.

Upvotes: 1

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