Daftar Properti dan Pengarsipan
Pelajari cara menyimpan dan memuat struktur data sederhana menggunakan NSUserDefaults, daftar properti, dan NSKeyedArchiver.
Daftar Properti dan Pengarsipan adalah pelajaran Objective-C iOS Development for Legacy & Enterprise Apps gratis di CoddyKit. Ini adalah pelajaran 1 dari 4. Kamu bisa membaca pelajaran lengkapnya di bawah secara gratis — lalu praktikkan langsung di browser dengan editor kode bawaan dan tutor AI 24/7. Ini adalah bagian dari jalur belajar Objective-C iOS Development for Legacy & Enterprise Apps, dan progresmu tersinkronisasi di web dan aplikasi CoddyKit. Kursus Objective-C iOS Development for Legacy & Enterprise Apps mencakup 4 pelajaran total.
Bagian dari pelajaran ini belum diterjemahkan dan ditampilkan dalam bahasa Inggris.
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!
Pertanyaan yang Sering Diajukan
Apakah pelajaran “Daftar Properti dan Pengarsipan” gratis?
Ya — teks lengkap “Daftar Properti dan Pengarsipan” gratis dibaca di sini di web. Untuk praktiknya secara interaktif (editor kode bawaan dan tutor AI 24/7) dan buka sisa kursus Objective-C iOS Development for Legacy & Enterprise Apps, upgrade ke CoddyKit PRO. Kursus Objective-C iOS Development for Legacy & Enterprise Apps mencakup 4 pelajaran total.
Apa yang akan aku pelajari di “Daftar Properti dan Pengarsipan”?
Pelajari cara menyimpan dan memuat struktur data sederhana menggunakan NSUserDefaults, daftar properti, dan NSKeyedArchiver. Kamu berlatih Objective-C iOS Development for Legacy & Enterprise Apps dengan kode praktik yang langsung kamu jalankan di browser, dan tutor AI 24/7 menjawab pertanyaanmu saat kamu mengerjakan pelajaran ini.
Apakah aku perlu pengalaman untuk memulai Objective-C iOS Development for Legacy & Enterprise Apps?
Tidak diperlukan pengalaman sebelumnya. Objective-C iOS Development for Legacy & Enterprise Apps di CoddyKit dirancang untuk pemula hingga pelajar tingkat lanjut, jadi kamu bisa memulai di sini atau dari awal dan belajar sesuai kecepatan kamu sendiri. Ini adalah pelajaran 1 dari 4.
Berapa lama pelajaran “Daftar Properti dan Pengarsipan” memakan waktu?
Sebagian besar pelajaran CoddyKit memakan waktu sekitar 5–10 menit. Setiap pelajaran ringkas dan interaktif, jadi kamu membuat kemajuan stabil dan melanjutkan dari tempat kamu tinggalkan di web dan aplikasi.
Bisakah aku menulis dan menjalankan kode dalam pelajaran Objective-C iOS Development for Legacy & Enterprise Apps ini?
Ya. Setiap pelajaran Objective-C iOS Development for Legacy & Enterprise Apps menyertakan editor kode bawaan, jadi kamu menulis dan menjalankan kode nyata langsung di browser dan mendapatkan umpan balik AI instan — tidak diperlukan penyiapan lokal.
Semua pelajaran dalam kursus ini
- Daftar Properti dan Pengarsipan
- Dasar-Dasar Core Data
- Integrasi SQLite dengan FMDB
- Menyimpan Preferensi dengan NSUserDefaults