속성 목록과 보관
NSUserDefaults, 속성 목록 및 NSKeyedArchiver를 사용해 간단한 데이터 구조를 저장하고 불러오는 방법을 배웁니다.
속성 목록과 보관은(는) CoddyKit의 무료 Objective-C iOS Development for Legacy & Enterprise Apps 강의입니다. 이것은 4개 중 1번째 강의입니다. 아래에서 전체 강의를 무료로 읽을 수 있으며, 내장 코드 에디터와 24/7 AI 튜터와 함께 브라우저에서 직접 실습할 수 있습니다. 이 강의는 Objective-C iOS Development for Legacy & Enterprise Apps 학습 경로의 일부이며, 진행 상황이 웹과 CoddyKit 앱에 동기화됩니다. Objective-C iOS Development for Legacy & Enterprise Apps 강의에는 총 4개의 강의가 포함되어 있습니다.
이 강의의 일부는 아직 번역되지 않았으며 영어로 표시됩니다.
Why Data Persistence?
When your app closes, all its in-memory data disappears. To keep user settings, game progress, or other important information, you need data persistence.
Data persistence means saving data to a permanent storage location, like a file on the device, so it can be retrieved later.
Understanding Property Lists
Property Lists (PLists) are a standard way for iOS apps to store structured data. They're XML or binary files that represent common data types.
- Supported Types:
NSString,NSNumber,NSDate,NSData,NSArray,NSDictionary. - PLists are great for small, hierarchical data like user preferences or configuration settings.
NSUserDefaults for Simple Data
NSUserDefaults is a convenient way to store small amounts of data, typically user preferences or application settings.
It works like a dictionary, saving key-value pairs directly to a Property List file managed by the system. It's ideal for simple data types.
Saving with NSUserDefaults
To save data using NSUserDefaults, you get the standard user defaults object and then use methods like setObject:forKey: or setInteger:forKey:.
The synchronize method (though often not strictly necessary in modern iOS) ensures data is written to disk immediately.
#import <Foundation/Foundation.h>
int main(int argc, const char * argv[]) {
@autoreleasepool {
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
// Save a string
[defaults setObject:@"CoddyKit User" forKey:@"username"];
// Save an integer
[defaults setInteger:123 forKey:@"userScore"];
// Optional: Ensure data is written immediately
[defaults synchronize];
NSLog(@"Data saved to NSUserDefaults!");
}
return 0;
}Loading with NSUserDefaults
Retrieving data is just as easy! Use methods like stringForKey: or integerForKey: with the same keys you used for saving.
Remember that if a key doesn't exist, you'll get nil for objects or a default value (like 0 for integers).
#import <Foundation/Foundation.h>
int main(int argc, const char * argv[]) {
@autoreleasepool {
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
// Load a string
NSString *username = [defaults stringForKey:@"username"];
// Load an integer
NSInteger userScore = [defaults integerForKey:@"userScore"];
NSLog(@"Loaded Username: %@", username ? username : @"(Not set)");
NSLog(@"Loaded User Score: %ld", (long)userScore);
}
return 0;
}Beyond NSUserDefaults
While NSUserDefaults is great for simple data, it has limitations:
- Not suitable for large amounts of data.
- Only handles Property List compatible types.
- Doesn't easily store custom objects (unless converted to
NSData).
For more complex data, especially custom objects, we need a different approach: Archiving.
Archiving Custom Objects
Archiving allows you to convert complex object graphs (like instances of your custom classes) into a flattened, binary representation (NSData).
This NSData can then be saved to a file or even stored in NSUserDefaults. The key player here is the NSCoding protocol and NSKeyedArchiver.
Implementing NSCoding Protocol
To make your custom Objective-C objects archivable, they must conform to the NSCoding protocol.
This involves implementing two methods: encodeWithCoder: (to save properties) and initWithCoder: (to load properties).
#import <Foundation/Foundation.h>
@interface GameScore : NSObject <NSCoding>
@property (nonatomic, strong) NSString *playerName;
@property (nonatomic) NSInteger score;
@end
@implementation GameScore
- (instancetype)initWithPlayerName:(NSString *)name score:(NSInteger)value {
self = [super init];
if (self) {
_playerName = name;
_score = value;
}
return self;
}
// Save properties to the coder
- (void)encodeWithCoder:(NSCoder *)coder {
[coder encodeObject:self.playerName forKey:@"playerName"];
[coder encodeInteger:self.score forKey:@"score"];
}
// Load properties from the coder
- (instancetype)initWithCoder:(NSCoder *)coder {
self = [super init];
if (self) {
_playerName = [coder decodeObjectForKey:@"playerName"];
_score = [coder decodeIntegerForKey:@"score"];
}
return self;
}
- (NSString *)description {
return [NSString stringWithFormat:@"Player: %@, Score: %ld", self.playerName, (long)self.score];
}
@endArchiving with NSKeyedArchiver
Once your custom class conforms to NSCoding, you can use NSKeyedArchiver to convert an object into NSData.
This example shows how to create a GameScore object and archive it. The resulting NSData can then be written to a file.
#import <Foundation/Foundation.h>
// GameScore class (from previous scene)
@interface GameScore : NSObject <NSCoding>
@property (nonatomic, strong) NSString *playerName;
@property (nonatomic) NSInteger score;
@end
@implementation GameScore
- (instancetype)initWithPlayerName:(NSString *)name score:(NSInteger)value { self = [super init]; if (self) { _playerName = name; _score = value; } return self; }
- (void)encodeWithCoder:(NSCoder *)coder { [coder encodeObject:self.playerName forKey:@"playerName"]; [coder encodeInteger:self.score forKey:@"score"]; }
- (instancetype)initWithCoder:(NSCoder *)coder { self = [super init]; if (self) { _playerName = [coder decodeObjectForKey:@"playerName"]; _score = [coder decodeIntegerForKey:@"score"]; } return self; }
- (NSString *)description { return [NSString stringWithFormat:@"Player: %@, Score: %ld", self.playerName, (long)self.score]; }
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
GameScore *playerData = [[GameScore alloc] initWithPlayerName:@"Hero" score:1000];
NSError *error = nil;
NSData *archivedData = [NSKeyedArchiver archivedDataWithRootObject:playerData
requiringSecureCoding:NO
error:&error];
if (archivedData && !error) {
NSLog(@"GameScore object archived successfully! Data length: %lu bytes", (unsigned long)archivedData.length);
// In a real app, you'd save archivedData to a file, e.g.,
// [archivedData writeToFile:@"/tmp/game_score.data" atomically:YES];
} else {
NSLog(@"Archiving failed: %@", error);
}
}
return 0;
}Unarchiving with NSKeyedUnarchiver
To get your object back, you use NSKeyedUnarchiver to convert the NSData back into an object.
This process calls the initWithCoder: method of your NSCoding-conforming class, reconstructing the object.
#import <Foundation/Foundation.h>
// GameScore class (from previous scene)
@interface GameScore : NSObject <NSCoding>
@property (nonatomic, strong) NSString *playerName;
@property (nonatomic) NSInteger score;
@end
@implementation GameScore
- (instancetype)initWithPlayerName:(NSString *)name score:(NSInteger)value { self = [super init]; if (self) { _playerName = name; _score = value; } return self; }
- (void)encodeWithCoder:(NSCoder *)coder { [coder encodeObject:self.playerName forKey:@"playerName"]; [coder encodeInteger:self.score forKey:@"score"]; }
- (instancetype)initWithCoder:(NSCoder *)coder { self = [super init]; if (self) { _playerName = [coder decodeObjectForKey:@"playerName"]; _score = [coder decodeIntegerForKey:@"score"]; } return self; }
- (NSString *)description { return [NSString stringWithFormat:@"Player: %@, Score: %ld", self.playerName, (long)self.score]; }
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
// Simulate archived data (in a real app, you'd load from a file)
GameScore *originalPlayerData = [[GameScore alloc] initWithPlayerName:@"Hero" score:1000];
NSData *archivedData = [NSKeyedArchiver archivedDataWithRootObject:originalPlayerData requiringSecureCoding:NO error:nil];
if (archivedData) {
NSError *error = nil;
GameScore *loadedPlayerData = [NSKeyedUnarchiver unarchivedObjectOfClass:[GameScore class]
fromData:archivedData
error:&error];
if (loadedPlayerData && !error) {
NSLog(@"Unarchived Player Data: %@", loadedPlayerData);
NSLog(@"Player Name: %@", loadedPlayerData.playerName);
NSLog(@"Score: %ld", (long)loadedPlayerData.score);
} else {
NSLog(@"Unarchiving failed: %@", error);
}
} else {
NSLog(@"Archiving failed, cannot unarchive.");
}
}
return 0;
}Quick Check: Data Storage
Which of the following is BEST suited for storing a user's 'dark mode' preference (a simple boolean value) in an Objective-C iOS app?
Recap & Next Steps
Great job! You've learned the fundamentals of data persistence in Objective-C:
- Property Lists (PLists): XML/binary files for structured data.
- NSUserDefaults: Ideal for small user preferences and settings using key-value pairs.
- NSCoding & NSKeyedArchiver: For converting custom objects into
NSDatafor storage and retrieval.
These methods are crucial for making your apps remember information between sessions. Next, we'll explore Core Data for more robust object graph management!
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자주 묻는 질문
“속성 목록과 보관” 강의는 무료인가요?
네 — “속성 목록과 보관” 전체 내용을 이 웹사이트에서 무료로 읽을 수 있습니다. 인터랙티브하게 실습하려면(내장 코드 에디터와 24/7 AI 튜터), CoddyKit PRO로 업그레이드하면 Objective-C iOS Development for Legacy & Enterprise Apps 강의 전체를 잠금 해제할 수 있습니다. Objective-C iOS Development for Legacy & Enterprise Apps 강의에는 총 4개의 강의가 포함되어 있습니다.
“속성 목록과 보관”에서 뭘 배우나요?
NSUserDefaults, 속성 목록 및 NSKeyedArchiver를 사용해 간단한 데이터 구조를 저장하고 불러오는 방법을 배웁니다. 브라우저에서 직접 실행하는 실습 코드로 Objective-C iOS Development for Legacy & Enterprise Apps을(를) 배우며, 24/7 AI 튜터가 강의를 진행하면서 질문에 답변해줍니다.
Objective-C iOS Development for Legacy & Enterprise Apps을(를) 시작하는 데 경험이 필요한가요?
사전 경험은 필요하지 않습니다. CoddyKit의 Objective-C iOS Development for Legacy & Enterprise Apps은(는) 초급자부터 고급 학습자까지를 위해 구성되어 있으므로, 여기서 시작하거나 처음부터 시작할 수 있으며 자신의 속도대로 진행할 수 있습니다. 이것은 4개 중 1번째 강의입니다.
“속성 목록과 보관” 강의는 얼마나 걸리나요?
대부분의 CoddyKit 강의는 약 5~10분이 소요됩니다. 각 강의는 간결하고 인터랙티브하여 꾸준한 진행이 가능하며, 웹과 앱에서 중단한 부분부터 바로 시작할 수 있습니다.
이 Objective-C iOS Development for Legacy & Enterprise Apps 강의에서 코드를 작성하고 실행할 수 있나요?
네. 모든 Objective-C iOS Development for Legacy & Enterprise Apps 강의에는 내장 코드 에디터가 포함되어 있으므로, 브라우저에서 바로 실제 코드를 작성하고 실행한 후 즉시 AI 피드백을 받을 수 있습니다 — 로컬 설정이 필요 없습니다.