Problem creating NSManagedObject derived class

I am doing something wrong here... I know that

I'm using Xcode and I have created the following class using the data modeller:

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>


@interface Project : NSManagedObject {
@private
}
@property (nonatomic, retain) NSNumber * indent;
@property (nonatomic, retain) NSNumber * collapsed;
@property (nonatomic, retain) NSString * color;
@property (nonatomic, retain) NSNumber * project_id;
@property (nonatomic, retain) NSNumber * item_order;
@property (nonatomic, retain) NSNumber * cache_count;
@property (nonatomic, retain) NSNumber * user_id;
@property (nonatomic, retain) NSString * name;

@end

When I am trying to propagate this class with data from a JSON source using the following code:

NSString* filePath = [[NSBundle mainBundle] pathForResource:@"projects" ofType:@"json"];

if (filePath) {
    NSString* jsonString = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil];
    DLog(@"JSON for Projects:%@", jsonString);
    SBJsonParser* jsonParser = [SBJsonParser new];
    id response = [jsonParser objectWithString:jsonString];
    NSArray* array = (NSArray*) response;
    NSEnumerator* e = [array objectEnumerator];
    NSDictionary* dictionary;
    while ((dictionary = (NSDictionary*)[e nextObject])) {

        Project* project = [[Project alloc] init];
        project.user_id = [dictionary objectForKey:@"user_id"];
        project.name = [dictionary objectForKey:@"name"];
        project.color = [dictionary objectForKey:@"color"];
        project.collapsed = [dictionary objectForKey:@"collapsed"];
        project.item_order = [dictionary objectForKey:@"item_order"];
        project.cache_count = [dictionary开发者_如何转开发 objectForKey:@"cache_count"];
        project.indent = [dictionary objectForKey:@"indent"];
        project.project_id = [dictionary objectForKey:@"project_id"];

        [elementArray addObject:project];

        [project release];
    }
}

However, the code stops at the project.user_id = [dictionary objectForKey:@"user_id"]; line with an exception "* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Project setUser_id:]: unrecognized selector sent to instance 0x590bcb0'"

I don't know why this is happening or how to resolve this.

I've set up a reality distortion field so I don't violate my NDA. And now I can answer your question, it has nothing to do with the product-that-must-not-be-named anyway.

There is your bug: Project* project = [[Project alloc] init];

The @dynamic setters and getters are not created for you if you create your object this way.
You can't use NSManagedObjects without a NSManagedObjectContext.

You should use something like this:

Project *project = (Project *)[NSEntityDescription insertNewObjectForEntityForName:@"Project" inManagedObjectContext:self.managedObjectContext];

Property names with underscores are not very sensible in the Objective C world - I guess the properties generated by Core Data have the wrong names therefore. Try using CamelCase, that is calling your properties userID, itemOrder, cacheCount etc.

You may need to set up your getters and setters.

It could be as simple as adding: @synthesize user_id;

In your class file.