AwesomeDataPersistenceHandler.m

//
//  AwesomeDataPersistenceHandler.m
//  awesomesauce
//
//  Created by Keegan Poppen on 3/31/11.
//  Copyright 2011 Lord Keeganus Industries. All rights reserved.
//

#import "AwesomeDataPersistenceHandler.h"
#import "JSON.h"


@implementation AwesomeDataPersistenceHandler

-(id)init {
	self = [super init];
	
	if (self) {
		//do stuff
	}
	
	return self;
}


- (void)dealloc {
	[managedObjectContext_ release];
    [managedObjectModel_ release];
    [persistentStoreCoordinator_ release];
	
	[super dealloc];
}


-(NSArray*)getAllSavedCompositions {
	NSDictionary *entities = [[self managedObjectModel] entitiesByName];
	NSEntityDescription *entity = [entities valueForKey:@"Composition"];
	
	NSFetchRequest *fetchRequest = [[[NSFetchRequest alloc] init] autorelease];
	[fetchRequest setEntity:entity];
	
	NSError *err;
	NSArray *results = [[self managedObjectContext] executeFetchRequest:fetchRequest error:&err];
	if (err != nil) {
		NSLog(@"fetch request error: %@", err);
	} else {
		NSLog(@"successfully fetched all %d results", [results count]);
	}
	
	NSMutableArray *titles = [[NSMutableArray alloc] init];
	
	for (unsigned i = 0; i < [results count]; ++i) {
		//[titles addObject:[results objectAtIndex:i]
		NSLog(@"obj: %@", [[results objectAtIndex:i] description]);
	}
	
	return [titles autorelease];
}


-(Composition*)getManagedObjectForComposition:(NSString*)title {
	NSDictionary *entities = [[self managedObjectModel] entitiesByName];
	NSEntityDescription *entity = [entities valueForKey:@"Composition"];
	
	NSFetchRequest *fetchRequest = [[[NSFetchRequest alloc] init] autorelease];
	[fetchRequest setEntity:entity];
	
	NSPredicate *predicate = [NSPredicate predicateWithFormat:@"title == %@",title];
	[fetchRequest setPredicate:predicate];
	
	NSError *err;
	NSArray *results = [[self managedObjectContext] executeFetchRequest:fetchRequest error:&err];
	if (err != nil) {
		NSLog(@"fetch request error: %@", err);
	} else {
		NSLog(@"I a'got'a the a'data, Mario! All %d of them.", [results count]);
	}
	
	return ([results count] == 1)? [results objectAtIndex:0] : nil;
}


-(NSDictionary*)getDataForComposition:(NSString*)title {
	Composition *obj = [self getManagedObjectForComposition:title];
	
	if(obj == nil) return nil;
	
	SBJsonParser *parser = [[[SBJsonParser alloc] init] autorelease];
	return [parser objectWithString:obj.data];	
}


-(void)setData:(NSDictionary*)data forComposition:(NSString*)title {
	Composition *composition = [self getManagedObjectForComposition:title];
	
	if (composition == nil) {
		composition = [NSEntityDescription insertNewObjectForEntityForName:@"Composition" inManagedObjectContext:[self managedObjectContext]];
		composition.title = title;
	}
	
	//store the data as a JSON-encoded string (yeah... really elegant...)
	SBJsonWriter *writer = [[[SBJsonWriter alloc] init] autorelease];
	composition.data = [[[writer stringWithObject:data] retain] autorelease];
	
	[self saveContext];
}


/**
 *
 * CoreData boilerplate
 *
 */


/**
 Returns the URL to the application's Documents directory.
 */
- (NSURL *)applicationDocumentsDirectory {
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}


- (void)saveContext {
    NSError *error = nil;
	NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    if (managedObjectContext != nil) {
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
            /*
             Replace this implementation with code to handle the error appropriately.
             
             abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
             */
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        } 
    }
} 


/**
 Returns the managed object context for the application.
 If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
 */
- (NSManagedObjectContext *)managedObjectContext {
    
    if (managedObjectContext_ != nil) {
        return managedObjectContext_;
    }
    
    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        managedObjectContext_ = [[NSManagedObjectContext alloc] init];
        [managedObjectContext_ setPersistentStoreCoordinator:coordinator];
    }
    return managedObjectContext_;
}


/**
 Returns the managed object model for the application.
 If the model doesn't already exist, it is created from the application's model.
 */
- (NSManagedObjectModel *)managedObjectModel {
    
    if (managedObjectModel_ != nil) {
        return managedObjectModel_;
    }
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"awesomedatamodel" withExtension:@"momd"];
    managedObjectModel_ = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];    
    return managedObjectModel_;
}


/**
 Returns the persistent store coordinator for the application.
 If the coordinator doesn't already exist, it is created and the application's store added to it.
 */
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
    
    if (persistentStoreCoordinator_ != nil) {
        return persistentStoreCoordinator_;
    }
    
    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"awesomedatamodel.sqlite"];
    
    NSError *error = nil;
    persistentStoreCoordinator_ = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![persistentStoreCoordinator_ addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
        /*
         Replace this implementation with code to handle the error appropriately.
         
         abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
         
         Typical reasons for an error here include:
         * The persistent store is not accessible;
         * The schema for the persistent store is incompatible with current managed object model.
         Check the error message to determine what the actual problem was.
         
         
         If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.
         
         If you encounter schema incompatibility errors during development, you can reduce their frequency by:
         * Simply deleting the existing store:
         [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]
         
         * Performing automatic lightweight migration by passing the following dictionary as the options parameter: 
         [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
         
         Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.
         
         */
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }    
    
    return persistentStoreCoordinator_;
}

@end