InAppSettings.h

#import <Foundation/Foundation.h>
@interface PassCodeSettings: NSObject<NSCoding>

@property (nonatomic, assign) BOOL isPasscodeEnabled;
@property (nonatomic, assign) NSUInteger attemptCount;
@property (nonatomic, assign) NSTimeInterval checkInterval;
@property (nonatomic, strong) NSDate *nextCheckDate;

@end

@interface InAppSettings : NSObject

@property (nonatomic, strong) NSString *applicationVersion;
@property (nonatomic, strong, readonly) PassCodeSettings *passCodeSettings;

+ (instancetype)defaultSettings;
- (void)savePasscodeSettings;

@end

InAppSettings.m

#import "InAppSettings.h"

NSString *const kApplicationVersion = @"kApplicationVersion";
NSString *const kPasscodeSettings = @"kPasscodeSettings";

@implementation InAppSettings

- (id)init {
    self = [super init];
    if (self) {
        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
        _applicationVersion = [defaults stringForKey:kApplicationVersion];
        
        NSData *passCodeData = [defaults dataForKey:kPasscodeSettings];        
        if (passCodeData) {
            _passCodeSettings = [NSKeyedUnarchiver unarchiveObjectWithData:passCodeData];
        } else {
            _passCodeSettings = [PassCodeSettings new];
        }        
    }
    
    return self;
}

+ (instancetype)defaultSettings {
    static InAppSettings *instance = nil;
    static dispatch_once_t onceToken = 0;
    dispatch_once(&onceToken, ^{
        instance = [InAppSettings new];
    });
    
    return instance;
}

- (void)setApplicationVersion:(NSString *)applicationVersion {
    [self willChangeValueForKey:@"applicationVersion"];
    _applicationVersion = applicationVersion;

    
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setObject:applicationVersion forKey:kApplicationVersion];
    [defaults synchronize];
    
    [self didChangeValueForKey:@"applicationVersion"];
}

- (void)savePasscodeSettings {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:_passCodeSettings] forKey:kPasscodeSettings];
    [defaults synchronize];
}

@end

@implementation PassCodeSettings

- (id)initWithCoder:(NSCoder *)aDecoder {
    self = [super init];
    if (self) {
        _attemptCount = [aDecoder decodeIntegerForKey:@"attemptCount"];
        _isPasscodeEnabled = [aDecoder decodeBoolForKey:@"isPassCodeEnabled"];
        _checkInterval = [aDecoder decodeDoubleForKey:@"checkInterval"];
        _nextCheckDate = [NSDate dateWithTimeIntervalSince1970:[aDecoder decodeDoubleForKey:@"nextCheckDate"]];
    }
   
    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder {
    [aCoder encodeBool:_isPasscodeEnabled forKey:@"isPassCodeEnabled"];
    [aCoder encodeInteger:_attemptCount forKey:@"attemptCount"];
    [aCoder encodeDouble:_checkInterval forKey:@"checkInterval"];
    [aCoder encodeDouble:[_nextCheckDate timeIntervalSince1970] forKey:@"nextCheckDate"];
}

@end