objective-c : using coredata helper class and fetchRequest

snippet.m

//using coredata helper class and fetchRequest

//appDelegate의 NSManagedObjectContext 참조

//TWCoreDataHelper.h

@interface TWCoreDataHelper : NSObject

+ (NSManagedObjectContext *)managedObjectContext;

@end


//TWCoreDataHelper.m

#import "TWCoreDataHelper.h"

@implementation TWCoreDataHelper

+ (NSManagedObjectContext *)managedObjectContext
{
    if (debug==1) {NSLog(@"Running %@ '%@'", self.class, NSStringFromSelector(_cmd));}
    
    NSManagedObjectContext *context = nil;
    
    id delegate = [[UIApplication sharedApplication] delegate];
    
    if ([delegate performSelector:@selector(managedObjectContext)]) {
        context = [delegate managedObjectContext];
    }
    
    return context; 
}

@end


//TWAlbumTableViewController.m

#import "TWCoreDataHelper.h" //코어데이터 헬퍼 클래스

@implementation TWAlbumTableViewController

- (void)viewWillAppear:(BOOL)animated
{
    if (debug==1) {NSLog(@"Running %@ '%@'", self.class, NSStringFromSelector(_cmd));}
    
    [super viewWillAppear:animated];
    
    //코어데이터 데이터 가져와서 테이블 뷰에 부리기
    
    NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Album"]; //give me all the Albums
    fetchRequest.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"date" ascending:NO]]; //arrange from newest to oldest
    
//    //코어데이터 헬퍼 클래스에서 담당
//    id delegate = [[UIApplication sharedApplication] delegate];
//    NSManagedObjectContext *context = [delegate managedObjectContext];
    
    NSError *error = nil;
    NSArray *fetchedAlbums = [[TWCoreDataHelper managedObjectContext] executeFetchRequest:fetchRequest
                                                                                    error:&error];
    
    self.albums = [fetchedAlbums mutableCopy]; //뮤터블 카피
    
    [self.tableView reloadData];
}