Uses NSKeyedArchiver and NSKeyedUnarchiver to save and load custom objects (Event) to and from the documents directory.

PersistenceDataManager.h

//
//  PersistenceDataManager.h
//  Events
//
//  Created by Alex Paul on 5/25/18.
//  Copyright © 2018 Alex Paul. All rights reserved.
//

#import "Event.h"

@interface PersistenceDataManager: NSObject

+ (NSArray *)loadEvents;
+ (BOOL)saveEvents:(NSArray *)events;
+ (BOOL)saveImageData:(NSData *)data withFilename:(NSString *)filename;
+ (UIImage *)imageWithFilename:(NSString *)filename;
+ (BOOL)deleteImageWithFilename:(NSString *)filename;

@end

PersistenceDataManager.m

//  PersistenceDataManager.m
//  Events
//
//  Created by Alex Paul on 5/25/18.
//  Copyright © 2018 Alex Paul. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "PersistenceDataManager.h"
#import "Event.h"

#define FILENAME @"favorites.plist"

@interface PersistenceDataManager ()
@end

@implementation PersistenceDataManager

#pragma mark Documents Directory
+ (NSString *)filepathWithName:(NSString *)filename {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = paths.firstObject;
    NSString *path = [documentsDirectory stringByAppendingPathComponent:filename];
    return path;
}

#pragma mark NSKeyedArchiver and NSKeyedUnarchiver
+ (BOOL)saveEvents:(NSArray *)events {
    NSString *path = [self filepathWithName:FILENAME];
    BOOL saved = [NSKeyedArchiver archiveRootObject:events toFile:path];
    return saved;
}

+ (NSArray *)loadEvents {
    NSString *path = [self filepathWithName:FILENAME];
    NSArray <Event *> *events = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
    return events;
}

#pragma mark Image Persistence
+ (BOOL)saveImageData:(NSData *)data withFilename:(NSString *)filename {
    NSString *path = [self filepathWithName:filename];
    NSError *error;
    BOOL saved = [data writeToFile:path options:NSDataWritingAtomic error:&error];
    if (error)
        saved = FALSE;
    return saved;
}

+ (BOOL)deleteImageWithFilename:(NSString *)filename {
    NSString *path = [self filepathWithName:filename];
    BOOL deleted = FALSE;
    if (path) {
        NSError *error;
        deleted = [[NSFileManager defaultManager] removeItemAtPath:path error:&error];
        if (error)
            deleted = FALSE;
    }
    return deleted;
}

+ (UIImage *)imageWithFilename:(NSString *)filename {
    NSString *path = [self filepathWithName:filename];
    UIImage *image;
    if (path) {
        image = [UIImage imageWithContentsOfFile:path];
    }
    return image;
}

@end