Helper functions for doing object serialization (to plist file)

ArchiveHelper.h

// ArchiveHelper.h
//
@interface ArchiveHelper : NSObject

+ (id)loadObjectFromFile:(NSString*)filePath withKey:(NSString*)key;

+ (void)saveObject:(id)object toFile:(NSString*)filePath withKey:(NSString*)key;

@end

ArchiveHelper.m

// ArchiveHelper.m
//
#import "ArchiveHelper.h"

+ (id)loadObjectFromFile:(NSString*)filePath withKey:(NSString*)key
{
    NSData* data = [[NSData alloc] initWithContentsOfFile:filePath];
    NSKeyedUnarchiver* ar = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];

	id object = [ar decodeObjectForKey:key];
	[ar finishDecoding];

	return object;
}

+ (void)saveObject:(id)object toFile:(NSString*)filePath withKey:(NSString*)key
{
	NSMutableData *data = [[NSMutableData alloc] init];
	NSKeyedArchiver *ar = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];

	[ar encodeObject:object forKey:key];
	[ar finishEncoding];

	[data writeToFile:filePath atomically:YES];
}

@end