iOS 数据持久化详解

文章来源:爱听音乐的狗博客

数据持久化方式:

1、属性列表(plist存储)

2、偏好设置(NSUserDefaults)

3、归档序列化存储

4、沙盒存储

5、Core Data

6、SQLite3

7、FMDB

8、Realm

应用场景及使用

1、属性列表(plist存储)
通常叫做plist文件,用于存储在程序中不经常修改、数据量小的数据,不支持自定义对象存储,支持数据存储的类型为:Array,Dictionary,String,Number,Data,Date,Boolean,通常用来存放接口名、城市名、银行名称、表情名等极少修改的数据

1.1 创建plist文件并添加数据

右击文件目录 ---> 选择"New File..." --->选择"Property List" ---> 输入plist文件名并在窗口中点击Create创建。在创建好的plist文件中选择Root类型并添加测试数据,如图所示:

创建.png
添加测试数据.png

1.2 获取plist文件数据

文件的类型为Array就使用数组获取,类型为Dictionary就使用字典方式获取数据,示例代码:

/**
 plist获取数据
 
 @param sender sender description
 */
- (IBAction)plistGetInfoButtonDidClicked:(UIButton *)sender {
    //获取plist文件路径
    NSString *path = [self getPlistFilePath];
    NSDictionary *dict = [[NSDictionary alloc] initWithContentsOfFile:path];
    NSLog(@"获取到的plist数据\n%@",dict);
}

/**
 获取plist文件路径

 @return 路径
 */
- (NSString *)getPlistFilePath {
    //获取plist文件路径
    NSString *path = [[NSBundle mainBundle] pathForResource:@"testProperty" ofType:@"plist"];
    return path;
}

2 偏好设置(NSUserDefaults)

用于存储用户的偏好设置,同样适合于存储轻量级的用户数据,数据会自动保存在沙盒的Libarary/Preferences目录下,本质上就是一个plist文件,所以同样的不支持自定义对象存储,支持数据存储的类型为:Array,Dictionary,String,Number,Data,Date,Boolean,可以用做检查版本是否更新、是否启动引导页、自动登录、版本号等等,需要注意的是NSUserDefaults是定时的将缓存中的数据写入磁盘,并不是即时写入,为了防止在写完NSUserDefaults后,程序退出导致数据的丢失,可以在写入数据后使用synchronize强制立即将数据写入磁盘

2.1 为NSUserDefaults创建分类

右击文件目录 ---> 选择"New File..." --->选择"Objective-C File" --->选择File Type方式、类并且输入名称

创建分类2.png

2.2 保存、获取数据示例:

#import 

NS_ASSUME_NONNULL_BEGIN

@interface NSUserDefaults (Category)


/**
 保存电话号码
 */
+ (void)savePhoneNumber:(NSString *)phoneNumber;

/**
 获取电话号码

 @return 电话号码
 */
+ (NSString *)getPhoneNumber;
@end

NS_ASSUME_NONNULL_END

#import "NSUserDefaults+Category.h"

static NSString * const phoneNumberKey = @"phoneNumberKey";

@implementation NSUserDefaults (Category)

#pragma mark - 电话号码
+ (void)savePhoneNumber:(NSString *)phoneNumber {
    [[NSUserDefaults standardUserDefaults] setObject:phoneNumber forKey:phoneNumberKey];
    [[NSUserDefaults standardUserDefaults] synchronize];
}
+ (NSString *)getPhoneNumber {
   return [[NSUserDefaults standardUserDefaults] objectForKey:phoneNumberKey];
}

3 归档序列化存储

归档可以直接将对象存储为文件,也可将文件直接解归档为对象,相对于plist文件与偏好设置数据的存储更加多样,支持自定义的对象存储,归档后的文件是加密的,也更加的安全,文件存储的位置可以自定义。

3.1 对象支持归档与解归档

创建HJPersonModel类继承自NSObject ,遵守NSCoding或者NSSecureCoding协议,重写两个方法。"supportsSecureCoding"是NSSecureCoding协议下的重要属性,如果采用NSSecureCoding协议,必须重写supportsSecureCoding 方法并返回YES

#import "HJPersonModel.h"

@interface HJPersonModel () 

@end

@implementation HJPersonModel

- (void)encodeWithCoder:(nonnull NSCoder *)aCoder {
    [aCoder encodeObject:_name forKey:@"name"];
    [aCoder encodeObject:@(_age) forKey:@"age"];
}

- (nullable instancetype)initWithCoder:(nonnull NSCoder *)aDecoder {
    if (self = [super init]) {
        self.name =  [aDecoder decodeObjectForKey:@"name"];
        self.age = [[aDecoder decodeObjectForKey:@"age"] integerValue];
    }
    return self;
}

+ (BOOL)supportsSecureCoding {
    return YES;
}

3.2 创建归档解归档工具

创建HJArchiveTool工具类继承自NSObject ,提供两个方法以实现归档解归档

#import "HJArchiveTool.h"

@implementation HJArchiveTool

#pragma mark - 归档解归档

+ (BOOL)archiveObject:(id)object prefix:(NSString *)prefix {
    if (!object)
        return NO;
    NSError *error;
    //会调用对象的encodeWithCoder方法
    NSData *data = [NSKeyedArchiver archivedDataWithRootObject:object
                          requiringSecureCoding:YES
                                          error:&error];
    if (error)
        return NO;
    
    [data writeToFile:[self getPathWithPrefix:prefix] atomically:YES];
    return YES;
}

+ (id)unarchiveClass:(Class)class prefix:(NSString *)prefix {
    
    NSError *error;
    NSData *data = [[NSData alloc] initWithContentsOfFile:[self getPathWithPrefix:prefix]];
    //会调用对象的initWithCoder方法
    id content = [NSKeyedUnarchiver unarchivedObjectOfClass:class fromData:data error:&error];
    if (error) {
        return nil;
    }
    return content;
}


/**
 存放的文件路径

 @return return value description
 */
+ (NSString *)getPathWithPrefix:(NSString *)prefix {
    
    NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
    NSString *filePathFolder = [documentPath stringsByAppendingPaths:@[@"archiveTemp"]].firstObject;
    if (![[NSFileManager defaultManager] fileExistsAtPath:filePathFolder]) {
        [[NSFileManager defaultManager] createDirectoryAtPath:filePathFolder withIntermediateDirectories:YES attributes:nil error:nil];
    }
    NSString *path = [NSString stringWithFormat:@"%@/%@.archive",filePathFolder,prefix];
    return path;
}

3.3 归档与解归档对象

HJPersonModel类对应的数据归档/解归档操作

#pragma mark - 归档解归档
/**
归档数据

@param sender sender description
*/
- (IBAction)archiveButtonDidClicked:(UIButton *)sender {
   HJPersonModel *model = [HJPersonModel new];
   model.name = @"小李子";
   model.age = 25;
   if ([HJArchiveTool archiveObject:model prefix:NSStringFromClass(model.class)]) {
       NSLog(@"归档成功");
   } else {
       NSLog(@"归档失败");
   }
}
/**
解归档数据

@param sender sender description
*/
- (IBAction)unarchiveButtonDidClicked:(UIButton *)sender {
   id content = [HJArchiveTool unarchiveClass:HJPersonModel.class prefix:NSStringFromClass(HJPersonModel.class)];
   NSLog(@"%@",content);
}

4 沙盒存储

可以提高程序的体验度,为用户节约数据流量,主要在用户阅读书籍、听音乐、看视频等,在沙盒中做数据的存储,主要包含文件夹:
Documents: 最常用的目录,存放重要的数据,iTunes同步时会备份该目录
Library/Caches: 一般存放体积大,不重要的数据,iTunes同步时不会备份该目录
Library/Preferences: 存放用户的偏好设置,iTunes同步时会备份该目录
tmp: 用于存放临时文件,在程序未运行时可能会删除该文件夹中的数据,iTunes同步时不会备份该目录

存放音乐文件示例:

4.1 创建HJSandBoxOperationTool工具类继承自NSObject,提供"保存音乐到沙盒路径"和"获取沙盒路径下的音乐"两个方法

#import "HJSandBoxOperationTool.h"


@implementation HJSandBoxOperationTool


/**
 保存音乐到沙盒路径

 @param musicUrlStr url地址
 */
+ (void)toolToSaveMusicToCache:(NSString *)musicUrlStr withMusicName:(NSString *)name {
    __weak typeof(self) weakSelf = self;
    dispatch_async(dispatch_queue_create("musicQueue", DISPATCH_QUEUE_PRIORITY_DEFAULT), ^{
        //已经存了
        if ([weakSelf alreadySaveMusic:name])
            return ;
        NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:musicUrlStr]];
        [data writeToFile:[weakSelf getPathWithMusicName:name] atomically:YES];
    });
}

/**
 获取沙盒路径下的音乐
 
 @param musicName 音乐名称
 @return 路径
 */
+ (NSString *)toolToGetMusicFromCache:(NSString *)musicName {
    NSString *musicPath = [self getPathWithMusicName:musicName];
    if ([[NSFileManager defaultManager] fileExistsAtPath:musicPath]) {
        return musicPath;
    }
    return nil;
}

/**
 获取沙盒路径下的音乐
 
 @return return value description
 */
+ (NSString *)getPathWithMusicName:(NSString *)name {
    
    NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
    NSString *filePathFolder = [documentPath stringsByAppendingPaths:@[@"music"]].firstObject;
    if (![[NSFileManager defaultManager] fileExistsAtPath:filePathFolder]) {
        [[NSFileManager defaultManager] createDirectoryAtPath:filePathFolder withIntermediateDirectories:YES attributes:nil error:nil];
    }
    NSString *path = [NSString stringWithFormat:@"%@/%@.mp3",filePathFolder,name];
    return path;
}


/**
 判断是否已经存储了音乐

 @param musicName 音乐名称
 @return return value description
 */
+ (BOOL)alreadySaveMusic:(NSString *)musicName {
    NSString *musicPath = [self getPathWithMusicName:musicName];
    if (![[NSFileManager defaultManager] fileExistsAtPath:musicPath]) {
        return NO;
    } else {
        NSData *data = [NSData dataWithContentsOfFile:musicPath];
        if (data.length > 0) {
            return YES;
        }
        return NO;
    }
}

4.2 工具类方法调用

#pragma mark - 沙盒存储

/**
 沙盒存数据

 @param sender sender description
 */
- (IBAction)sandBoxSaveButtonDidClicked:(UIButton *)sender {
    //musicUrl 为.mp3格式的音乐url地址
    [HJSandBoxOperationTool toolToSaveMusicToCache:musicUrl withMusicName:@"耳朵"];
}

/**
 沙盒取数据

 @param sender sender description
 */
- (IBAction)sendBoxGetInfoButtonDidClicked:(UIButton *)sender {
    NSString *str = [HJSandBoxOperationTool toolToGetMusicFromCache:@"耳朵"];
    NSLog(@"%@",str);
}

5 Core Data

Core Data是框架,并不是数据库,该框架提供了对象关系的映射功能,使得能够将OC对象转换成数据,将数据库中的数据还原成OC对象,在转换的过程中不需要编写任何的SQL语句,在Core Data中有三个重要的概念:

NSPersistentStoreCoordinator:持久化存储协调器,在NSPersistentStoreCoordinator中包含了持久化存储区,在持久化存储区中包含了数据表中的很多数据,持久化存储区的设置通常选择NSSQLiteStoreType,也就是选择SQLite数据库

NSManagedObjectModel:托管对象模型,用于描述数据结构的模型

NSManagedObjectContext:托管对象上下文,在上下文中包含多个托管对象,用于管理对象的生命周期,为何会出现NSManagedObjectContext,原因在于将对象转换成数据是保存到磁盘上的,磁盘与RAM之间传输数据是会有开销,并且磁盘读写的速度没有RAM快,通过托管对象上下文可以迅速的获取到数据,修改了数据之后,需要调用上下文的save方法,将数据写入到数据库中,也就是磁盘中

5.1 Core Data 文件的简单创建

右击文件夹 ---> 选择 "New File..." ---> 选择"Data Model" ---> 输入文件名称并创建。创建后缀名为.xcdatamodeld的模型文件后,添加实体,并在实体中添加属性及类别

创建Core Data文件.png

点击"Editor"菜单项 ---> 选择"Create NSManagedObject Subclass..."项--->选择创建的Data Model--->选择创建的实体类--->选择需要放置的文件目录--->点击"Create"创建托管对象类。

构建实体类.png

5.2 单利实例化CoreDataManager

创建HJCoreDataManager继承自NSObject,针对Core Data的基本操作进行封装。.h文件提供单利创建与删除数据库两个方法,.m文件为方法的实现

#import 
#import 


NS_ASSUME_NONNULL_BEGIN

@interface HJCoreDataManager : NSObject


/**
 单利创建

 @return HJCoreDataManager
 */
+ (instancetype)sharedInstanceManager;

/**
 删除数据库
 */
+ (void)managerForDelete;

//......

@end

NS_ASSUME_NONNULL_END
#import "HJCoreDataManager.h"

#define HJStrIsEmpty(str) ((str == nil) || ([str isEqualToString: @""]) || (str == NULL) ||     ([str isKindOfClass:[NSNull class]]))


@interface HJCoreDataManager ()


/**
 数据模型
 */
@property (nonatomic, strong) NSManagedObjectModel *objectModel;


/**
 持久化数据
 */
@property (nonatomic, strong) NSPersistentStoreCoordinator *coordinator;

/**
 管理数据的对象
 */
@property (nonatomic, strong) NSManagedObjectContext *objectContext;
@end

@implementation HJCoreDataManager

#pragma mark - 单利创建
+ (instancetype)sharedInstanceManager {
    static HJCoreDataManager *manager = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        manager = [[HJCoreDataManager alloc] init];
    });
    return manager;
}

- (instancetype)init {
    if (self = [super init]) {
        //创建托管对象模型
        NSURL *url = [[NSBundle mainBundle] URLForResource:@"HJCoreData" withExtension:@"momd"];
        _objectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:url];
        //创建持久化数据协调器
        _coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:_objectModel];
        //关联并创建本地数据库文件
        [_coordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[self dbPath] options:nil error:nil];
        //创建托管对象上下文
        _objectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:(NSMainQueueConcurrencyType)];
        [_objectContext setPersistentStoreCoordinator:_coordinator];
    }
    return self;
}


/**
 获取数据库路径

 @return return value description
 */
- (NSURL *)dbPath {
    NSString *documentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).lastObject;
    NSString *dbFolder = [documentPath stringByAppendingPathComponent:@"CoreData"];
    if (![[NSFileManager defaultManager] fileExistsAtPath:dbFolder]) {
        [[NSFileManager defaultManager] createDirectoryAtPath:dbFolder withIntermediateDirectories:YES attributes:nil error:nil];
    }
    NSURL *dbUrl = [[NSURL fileURLWithPath:dbFolder] URLByAppendingPathComponent:@"db.sqlite"];
    return dbUrl;
}

#pragma mark - 删除数据库
+ (void)managerForDelete {
    NSString *documentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject;
    NSString *filePath = [documentPath stringByAppendingPathComponent:@"CoreData"];
    if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
        [[NSFileManager defaultManager] removeItemAtPath:filePath error:nil];
    }
}

//......

@end

5.3 数据的增删改查

数据增删改查操作的基本封装,.h文件提供方法,.m文件实现方法,需要注意的是,在对数据进行了修改之后都要调用上下文的save方法,将数据写入到数据库中,也就是磁盘中

//================================ 添加数据 ================================//

/**
 获取数据模型

 @param entityName 数据模型类名称
 @return return value description
 */
+ (NSManagedObject *)getTableWithEntityName:(NSString * _Nonnull)entityName;

/**
 保存数据
 */
+ (BOOL)save;

//================================       ================================//

/**
 删除数据

 @param entityName   数据模型类名称
 @param searchString 属性名的值包含的字符
 @param attribute    属性名称
 @return             成功失败
 */
+ (BOOL)deleteByEntityName:(NSString * _Nonnull)entityName
               withMaching:(NSString * _Nonnull)searchString
             withAttribute:(NSString * _Nonnull)attribute;

/**
 更新数据

 @param managedObject pojo对象
 @return bool
 */
+ (BOOL)updateManagedObject:(NSManagedObject *)managedObject;

/**
 查询数据

 @param entityName   数据模型类名称
 @param searchString 属性名的值包含的字符
 @param attribute    属性名称
 @param sortArribute 按哪个属性名称排序
 @param ascending    是否升序
 @return             模型数组
 */
+ (NSArray *)selectByEntityName:(NSString * _Nonnull)entityName
                    withMaching:(NSString * _Nullable)searchString
                  withAttribute:(NSString * _Nullable)attribute
                      sortingBy:(NSString * _Nullable)sortArribute
                    isAscending:(BOOL)ascending;
#pragma mark - 获取数据模型
+ (NSManagedObject *)getTableWithEntityName:(NSString *)entityName {
    NSManagedObject *managedObject = [NSEntityDescription insertNewObjectForEntityForName:entityName inManagedObjectContext:[HJCoreDataManager sharedInstanceManager].objectContext];
    return managedObject;
}

#pragma mark - 保存数据
+ (BOOL)save {
    NSError *error;
    BOOL success = [[HJCoreDataManager sharedInstanceManager].objectContext save:&error];
    return success;
}

#pragma mark - 删除数据
+ (BOOL)deleteByEntityName:(NSString * _Nonnull)entityName
               withMaching:(NSString * _Nonnull)searchString
             withAttribute:(NSString * _Nonnull)attribute {
    //没有输入删除条件
    if (HJStrIsEmpty(attribute) || HJStrIsEmpty(searchString)) {
        return YES;
    }
    //查询数据
    NSArray *array = [self selectByEntityName:entityName
                                  withMaching:searchString
                                withAttribute:attribute
                                    sortingBy:attribute
                                  isAscending:YES];
    if (array.count > 0) {
        //删除
        for (NSManagedObject *object in array) {
            [[HJCoreDataManager sharedInstanceManager].objectContext deleteObject:object];
        }
    }
    //执行保存操作
    return [HJCoreDataManager save];
}

#pragma mark - 更新数据
+ (BOOL)updateManagedObject:(NSManagedObject *)managedObject {
    [[HJCoreDataManager sharedInstanceManager].objectContext refreshObject:managedObject mergeChanges:YES];
    return [HJCoreDataManager save];
}

#pragma mark - 查询数据
+ (NSArray *)selectByEntityName:(NSString * _Nonnull)entityName
                    withMaching:(NSString * _Nullable)searchString
                  withAttribute:(NSString * _Nullable)attribute
                      sortingBy:(NSString * _Nullable)sortArribute
                    isAscending:(BOOL)ascending{
    NSEntityDescription *entity = [NSEntityDescription entityForName:entityName inManagedObjectContext:[HJCoreDataManager sharedInstanceManager].objectContext];
    //创建fetch请求
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    fetchRequest.entity = entity;
    //一次性获取完
    [fetchRequest setFetchBatchSize:0];
    if (!HJStrIsEmpty(sortArribute)) {
        //排序
        NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:sortArribute ascending:ascending selector:nil];
        NSArray *descriptors = @[sortDescriptor];
        fetchRequest.sortDescriptors = descriptors;
    } else {
        fetchRequest.sortDescriptors = @[];
    }
    
    if (!HJStrIsEmpty(searchString) && !HJStrIsEmpty(attribute)) {
        //某个属性的值包含某个字符串
        //%K 某个属性的值
        //%@ 传递过来的字符串
        //模糊查询 contains[cd] 包含某个值 c标识忽略大小写,d标识忽略重音
        //查询 ==
        fetchRequest.predicate = [NSPredicate predicateWithFormat:@"%K == %@",attribute, searchString];
    }
    NSError *error;
    NSFetchedResultsController *fetchedController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:[HJCoreDataManager sharedInstanceManager].objectContext sectionNameKeyPath:nil cacheName:nil];
    //执行获取操作
    if ([fetchedController performFetch:&error]) {
        //获取数据
        return [fetchedController fetchedObjects];
    } else {
        return @[];
    }
}

5.4 数据操作例子

封装了之后,调用数据的增删改查就会更加的方便,程序启动后,在"- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions"方法中去调用 "[HJCoreDataManager sharedInstanceManager];"初始化对象,然后根据需求调用所封装的操作数据方法进行读写操作。增删改查示例:

#pragma mark - Core Data数据操作


/**
 增加数据

 @param sender sender description
 */
- (IBAction)coreDataAddInfoButtonDidClicked:(UIButton *)sender {

    HJCarModel *carModel = (HJCarModel *)[HJCoreDataManager getTableWithEntityName:NSStringFromClass([HJCarModel class])];
    carModel.carName = @"AE99";
    carModel.userName = @"一个大孩子";
    carModel.userID = 11;
    [HJCoreDataManager save];
}

/**
 删除数据

 @param sender sender description
 */
- (IBAction)coreDataDeleteInfoButtonDidClicked:(UIButton *)sender {
    BOOL isSuccess = [HJCoreDataManager deleteByEntityName:NSStringFromClass([HJCarModel class])
                                   withMaching:@"AE99"
                                 withAttribute:@"carName"];
    NSLog(@"%d",isSuccess);
}


/**
 修改数据

 @param sender sender description
 */
- (IBAction)coreDataUpdateInfoButtonDidClicked:(UIButton *)sender {
    //修改已经保存到数据库中的数据,在修改之前我们应该获取要修改的数据,修改之后对数据进行再次保存
    NSArray *array = [HJCoreDataManager selectByEntityName:NSStringFromClass([HJCarModel class])
                                     withMaching:nil
                                   withAttribute:nil
                                       sortingBy:@"userID"
                                     isAscending:YES];
    HJCarModel *model = array.firstObject;
    model.userName = @"爱听话的孩子";
    BOOL isSuccess = [HJCoreDataManager updateManagedObject:model];
    NSLog(@"%d",isSuccess);
}

/**
 查询数据

 @param sender sender description
 */
- (IBAction)coreDataSelectInfoButtonDidClicked:(UIButton *)sender {
    NSArray *array = [HJCoreDataManager selectByEntityName:NSStringFromClass([HJCarModel class])
                                     withMaching:nil
                                   withAttribute:nil
                                       sortingBy:nil
                                     isAscending:YES];
    if (array.count > 0) {
        for (HJCarModel *model in array) {
            NSLog(@"%@---%@---%lld", model.userName,model.carName,model.userID);
        }
    }
    
}

6 SQLite3

SQLite是轻量级的数据库,占用资源很少,最初是用于嵌入式的系统,在iOS中使用SQLite,需要加入"libsqlite3.tbd"依赖库并导入头文件。不应该频繁的打开关闭数据库,有可能会影响性能, 应在启动程序时打开数据库,在退出程序是关闭数据库

6.1 封装SQLite3

创建名为HJSQLiteDBManager的类继承自NSObject,导入sqlite3头文件,.h提供操作数据库方法,.m是方法的实现

#import 


NS_ASSUME_NONNULL_BEGIN

@interface HJSQLiteDBManager : NSObject

/**
 单利创建Manager

 @return return value description
 */
+ (instancetype)sharedInstance;

/**
 打开数据库
 */
+ (void)openDB;

/**
 关闭数据库
 */
+ (void)closeDB;

/**
 删除数据库

 @return BOOL
 */
+ (BOOL)deleteSQliteDB;

/**
 创建表

 @param sql sql语句
 @return BOOL
 */
+ (BOOL)createTableWithSql:(NSString *)sql;

/**
 增删改操作
 
 @param sql sql语句
 @return BOOL
 */
+ (BOOL)operationRecordWithSql:(NSString *)sql;

/**
 查询记录

 @param sql sql语句
 @return NSArray
 */
+ (NSArray *)selectRecordWithSql:(NSString *)sql;
@end

NS_ASSUME_NONNULL_END

//  首先在build phases中去导入libsqlite3.tbd
//
//  不应该频繁的打开关闭数据库,有可能会影响性能
//  在启动程序时打开数据库
//  在退出程序是关闭数据库
//  sqlite3_exec() 就是把提到的三个函数结合在了一起:sqlite3_step(), sqlite3_perpare(), sqlite3_finalize()
#import "HJSQLiteDBManager.h"
#import 

@interface HJSQLiteDBManager ()

@property (nonatomic, assign) sqlite3 *db;

@end

@implementation HJSQLiteDBManager

#pragma mark - 创建对象
+ (instancetype)sharedInstance {
    static HJSQLiteDBManager *manager = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        manager = [[HJSQLiteDBManager alloc] init];
    });
    return manager;
}
- (instancetype)init {
    if (self = [super init]) {

    }
    return self;
}
#pragma mark - 打开数据库
+ (void)openDB {
    sqlite3 *sql = [HJSQLiteDBManager sharedInstance].db;
    sqlite3_open([[HJSQLiteDBManager getDBpath] UTF8String], &sql);
    [HJSQLiteDBManager sharedInstance].db = sql;
}

+ (NSString *)getDBpath {
    NSString *documentStr = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject;
    NSString *sqlDBFolder = [documentStr stringByAppendingPathComponent:@"SQLiteDB"];
    if (![[NSFileManager defaultManager] fileExistsAtPath:sqlDBFolder]) {
        [[NSFileManager defaultManager] createDirectoryAtPath:sqlDBFolder withIntermediateDirectories:YES attributes:nil error:nil];
    }
    return [sqlDBFolder stringByAppendingPathComponent:@"dataDemo.sqlite"];
}

#pragma mark - 关闭数据库
+ (void)closeDB {
    sqlite3_close([HJSQLiteDBManager sharedInstance].db);
}

#pragma mark - 删除数据库
+ (BOOL)deleteSQliteDB {
    NSString *documentStr = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject;
    NSString *sqlDBFolder = [documentStr stringByAppendingPathComponent:@"SQLiteDB"];
    NSError *error;
    if ([[NSFileManager defaultManager] fileExistsAtPath:sqlDBFolder]) {
        [[NSFileManager defaultManager] removeItemAtPath:sqlDBFolder error:&error];
    }
    if (error) {
        return NO;
    }
    return YES;
}

#pragma mark - 创建表
+ (BOOL)createTableWithSql:(NSString *)sql {
    sqlite3 *sqlite = [[HJSQLiteDBManager sharedInstance] db];
    char *errorMsg = "";
    if (sqlite3_exec(sqlite, [sql UTF8String], nil, nil, &errorMsg) == SQLITE_OK) {
        return YES;
    } else {
        NSLog(@"创建表失败");
        return NO;
    }
}

#pragma mark - 查询
+ (NSArray *)selectRecordWithSql:(NSString *)sql {
    sqlite3_stmt *stmt;
    if (sqlite3_prepare_v2([HJSQLiteDBManager sharedInstance].db, [sql UTF8String], -1, &stmt, nil) == SQLITE_OK) {
        NSMutableArray *array = [NSMutableArray array];
        //执行sql语句
        while (sqlite3_step(stmt) == SQLITE_ROW) {
            //获取列数
            int columnCount = sqlite3_column_count(stmt);
            //获取每一列的值与列明放入字典数组中
            NSMutableDictionary *dict = [NSMutableDictionary dictionary];
            for (int i = 0; i < columnCount; i++) {
                //获取值
                char *value = (char *)sqlite3_column_text(stmt, i);
                NSString *valueStr;
                if (value != NULL) {
                    valueStr = [NSString stringWithUTF8String:value];
                }
                //获取key
                char *key = (char *)sqlite3_column_name(stmt, i);
                NSString *keyStr = [NSString stringWithUTF8String:key];
                dict[keyStr] = valueStr;
            }
            [array addObject:dict];
        }
        sqlite3_finalize(stmt);
        return array;
    }
    return @[];
}


/**
 增删改操作记录

 @param sql sql语句
 @return BOOL
 */
+ (BOOL)operationRecordWithSql:(NSString *)sql {
    //对sql执行预编译
    sqlite3_stmt *stmt;
    //sqlite3_prepare_v2是执行查询的方法
    if (sqlite3_prepare_v2([HJSQLiteDBManager sharedInstance].db, [sql UTF8String], -1, &stmt, nil) == SQLITE_OK) {
        //执行sql语句
        if (sqlite3_step(stmt) == SQLITE_DONE) {
            sqlite3_finalize(stmt);
            return YES;
        }
    }
    return NO;
}

@end

6.2 数据操作示例

封装之后,在"- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions"方法中去调用 "[HJSQLiteDBManager openDB];"打开数据库,然后根据需求调用所封装的操作数据方法进行读写操作。增删改查示例:

#pragma mark - SQLite3数据操作


/**
 添加数据

 @param sender sender description
 */
- (IBAction)sqlAddInfoButtonDidClicked:(UIButton *)sender {
    NSString *sqlStr = [NSString stringWithFormat:@"CREATE TABLE IF NOT EXISTS %@(userId INT PRIMARY KEY NOT NULL, name CHAR(20) NOT NULL, age INT)",NSStringFromClass([HJPersonModel class])];
    [HJSQLiteDBManager createTableWithSql:sqlStr];
    NSString *insetSql = [NSString stringWithFormat:@"INSERT INTO %@ (userId, name) VALUES (2, '小金人')", NSStringFromClass([HJPersonModel class])];
    [HJSQLiteDBManager operationRecordWithSql:insetSql];
}
/**
 删除数据
 
 @param sender sender description
 */
- (IBAction)sqlDeleteInfoButtonDidClicked:(UIButton *)sender {
    NSString *deleteSql = [NSString stringWithFormat:@"DELETE FROM %@ WHERE userId = 2", NSStringFromClass([HJPersonModel class])];
    [HJSQLiteDBManager operationRecordWithSql:deleteSql];
}
/**
 修改数据
 
 @param sender sender description
 */
- (IBAction)sqlUpdateInfoButtonDidClicked:(UIButton *)sender {
    NSString *updateSql = [NSString stringWithFormat:@"UPDATE %@ SET NAME = '小可爱', AGE = 90 WHERE userId = 2", NSStringFromClass([HJPersonModel class])];
    [HJSQLiteDBManager operationRecordWithSql:updateSql];
}
/**
 查询数据
 
 @param sender sender description
 */
- (IBAction)sqlSelectInfoButtonDidClicked:(UIButton *)sender {
    NSString *selectSql = [NSString stringWithFormat:@"SELECT * FROM %@", NSStringFromClass([HJPersonModel class])];
    NSArray *array = [HJSQLiteDBManager selectRecordWithSql:selectSql];
    NSLog(@"%@",array);
}

7 FMDB

FMDB以OC的方式封装了SQLite的C语言API,减去了冗余的C语言代码,使得API更具有OC的风格,更加的面向对象,相对于Core Data框架更加的轻量级,FMDB还提供了多线程安全的数据库操作方法,在FMDB中有三个重要的概念:

FMDatabase:一个FMDatabase就代表一个SQLite数据库,执行sql语句

FMResultSet:执行查询后的结果集

FMDatabaseQueue:用于在多线程中执行多个查询或更新,安全的

7.1 封装FMDB

FMDB的导入可以直接使用CocoaPods,导入后需要对其进行封装以拥有更加友好的API。创建HJFMDBManager类继承自NSObject,导入FMDatabase和FMDatabaseQueue类,.h文件中提供操作数据库方法,.m提供方法的实现

#import 

NS_ASSUME_NONNULL_BEGIN

@interface HJFMDBManager : NSObject

/**
 单利manager

 @return return value description
 */
+ (instancetype)sharedInstance;

/**
 打开数据库

 @return BOOL
 */
+ (BOOL)openDBForQueue;

/**
 关闭数据库
 */
+ (void)closeDBForQueue;



/**
 删除数据库

 @return BOOL
 */
+ (BOOL)deleteFMDB;


/**
 执行增删改建表

 @param sql sql语句
 */
+ (BOOL)executeWithSql:(NSString *)sql;

/**
 异步,执行增删改建表

 @param sql sql语句
 @param successBlock block
 */
+ (void)executeAsynWithSql:(NSString *)sql
                 isSuccess:(void(^)(BOOL isSuccess))successBlock;

/**
 执行查询数据
 
 @param sql sql语句
 */
+ (NSArray *)executeQueryWithSql:(NSString *)sql;

/**
 异步,执行查询数据

 @param sql sql语句
 @param successBlock block
 */
+ (void)executeAsynQueryWithSql:(NSString *)sql
                      isSuccess:(void(^)(NSArray *resultArray))successBlock;

@end

NS_ASSUME_NONNULL_END
#import "HJFMDBManager.h"
#import "fmdb/FMDatabase.h"
#import "fmdb/FMDatabaseQueue.h"

@interface HJFMDBManager ()

@property (nonatomic, strong) FMDatabase *db;
@property (nonatomic, strong) FMDatabaseQueue *dbQueue;

@end

@implementation HJFMDBManager

#pragma mark 创建manager
+ (instancetype)sharedInstance {
    static HJFMDBManager *manager;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        manager = [[HJFMDBManager alloc] init];
    });
    return manager;
}

#pragma mark - 打开数据库
+ (BOOL)openDBForQueue {
    //获取路径
    NSString *documentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject;
    //FMDB文件夹
    NSString *fmdbFolder = [documentPath stringByAppendingPathComponent:@"FMDB"];
    //判断文件夹是否存在
    if (![[NSFileManager defaultManager] fileExistsAtPath:fmdbFolder]) {
        [[NSFileManager defaultManager] createDirectoryAtPath:fmdbFolder withIntermediateDirectories:YES attributes:nil error:nil];
    }
    //数据库路径
    NSString *dbPath = [fmdbFolder stringByAppendingPathComponent:@"fmdb.db"];
    FMDatabase *db = [FMDatabase databaseWithPath:dbPath];
    if ([db open]) {
        [HJFMDBManager sharedInstance].db = db;
        [HJFMDBManager sharedInstance].dbQueue = [FMDatabaseQueue databaseQueueWithPath:dbPath];
        return YES;
    }
    return NO;
}

#pragma mark - 关闭数据库
+ (void)closeDBForQueue {
    [[[HJFMDBManager sharedInstance] dbQueue] close];
}

#pragma mark - 删除数据库
+ (BOOL)deleteFMDB {
    NSString *documentStr = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject;
    NSString *fmdbFolder = [documentStr stringByAppendingPathComponent:@"FMDB"];
    NSError *error;
    if ([[NSFileManager defaultManager] fileExistsAtPath:fmdbFolder]) {
        [[NSFileManager defaultManager] removeItemAtPath:fmdbFolder error:&error];
    }
    if (error) {
        return NO;
    }
    return YES;
}

#pragma mark - 执行增删改建表
+ (BOOL)executeWithSql:(NSString *)sql {
    return [[HJFMDBManager sharedInstance].db executeUpdate:sql];
}

#pragma mark - 异步,执行增删改建表
+ (void)executeAsynWithSql:(NSString *)sql
                     isSuccess:(void(^)(BOOL isSuccess))successBlock {
    [[[HJFMDBManager sharedInstance] dbQueue] inDatabase:^(FMDatabase * _Nonnull db) {
        BOOL isSuccess = [db executeUpdate:sql];
        if (successBlock) {
            successBlock(isSuccess);
        }
    }];
}

#pragma mark - 执行查询数据
+ (NSArray *)executeQueryWithSql:(NSString *)sql {
    FMResultSet *resultSet = [[HJFMDBManager sharedInstance].db executeQuery:sql];
    NSMutableArray *array = [NSMutableArray array];
    while (resultSet.next) {
        [array addObject:resultSet.resultDictionary];
    }
    return array;
}

#pragma mark - 异步,执行查询数据
+ (void)executeAsynQueryWithSql:(NSString *)sql
                      isSuccess:(void(^)(NSArray *resultArray))successBlock {
    [[[HJFMDBManager sharedInstance] dbQueue] inDatabase:^(FMDatabase * _Nonnull db) {
        FMResultSet *resultSet = [db executeQuery:sql];
        NSMutableArray *array = [NSMutableArray array];
        while (resultSet.next) {
            [array addObject:resultSet.resultDictionary];
        }
        if (successBlock) {
            successBlock(array);
        }
    }];
}

7.2 数据操作示例

在"- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions"方法中去调用 "[HJFMDBManager openDBForQueue];"打开数据库,然后根据需求调用所封装的操作数据方法进行读写操作。增删改查示例:

#pragma mark - FMDB数据库操作

/**
 增加记录

 @param sender sender description
 */
- (IBAction)fmdbInsertButtonDidClicked:(UIButton *)sender {
    NSString *creatStr =[NSString stringWithFormat:@"CREATE TABLE IF NOT EXISTS %@(userId INT PRIMARY KEY NOT NULL, name CHAR(20) NOT NULL, age INT)", NSStringFromClass([HJPersonModel class])];
    [HJFMDBManager executeAsynWithSql:creatStr isSuccess:^(BOOL isSuccess) {
        if (isSuccess) {
            NSLog(@"创建表成功");
        }
    }];
    NSString *insertStr = [NSString stringWithFormat:@"INSERT INTO %@ VALUES (2, '小金人', 25)", NSStringFromClass([HJPersonModel class])];
    [HJFMDBManager executeAsynWithSql:insertStr isSuccess:^(BOOL isSuccess) {
        if (isSuccess) {
            NSLog(@"插入数据成功");
        }
    }];
}
/**
 删除记录
 
 @param sender sender description
 */
- (IBAction)fmdbDeleteButtonDidClicked:(UIButton *)sender {
    NSString *insertStr = [NSString stringWithFormat:@"DELETE FROM %@ WHERE USERID = 2", NSStringFromClass([HJPersonModel class])];
    [HJFMDBManager executeAsynWithSql:insertStr isSuccess:^(BOOL isSuccess) {
        if (isSuccess) {
            NSLog(@"删除数据成功");
        }
    }];
}
/**
 修改记录
 
 @param sender sender description
 */
- (IBAction)fmdbUpdateButtonDidClicked:(UIButton *)sender {
    NSString *insertStr = [NSString stringWithFormat:@"UPDATE %@ SET userid = 11, NAME = '小可爱', AGE = 90 WHERE userId = 2", NSStringFromClass([HJPersonModel class])];
    [HJFMDBManager executeAsynWithSql:insertStr isSuccess:^(BOOL isSuccess) {
        if (isSuccess) {
            NSLog(@"修改数据成功");
        }
    }];
}
/**
 查询记录
 
 @param sender sender description
 */
- (IBAction)fmdbSelectButtonDidClicked:(UIButton *)sender {
    NSString *selectSql = [NSString stringWithFormat:@"SELECT * FROM %@", NSStringFromClass([HJPersonModel class])];
    [HJFMDBManager executeAsynQueryWithSql:selectSql
                                 isSuccess:^(NSArray * _Nonnull resultArray) {
                                     NSLog(@"%@",resultArray);
                                 }];
}

8 Realm

Realm是一款可以用于iOS(同样适用于Swift&Objective-C)和Android的跨平台移动数据库。Realm极大地减小了学习成本,没有Core Data与SQLite冗余、复杂的知识和代码,更加的面向对象。Realm还提供了一个轻量级的数据库查看工具"Realm Browser",可以非常简便的查看数据库当中的内容

8.1 Realm的安装

Realm的安装方法有很多种,使用 Dynamic Framework、CocoaPods等方法都行,这里仅介绍一种

1、下载最新的Realm版本,并解压,注意选择下载适用的语言,OC应选择下载 "realm-objc"版本

2、选择Xcode 工程的”General”设置项,从文件夹ios/dynamic/、osx/、tvos/或者watchos/中将’Realm.framework’拖曳到”Embedded Binaries”选项中。勾选上Copy items if needed,点击Finish按钮

3、选择 Target 的”Build Settings”中,在”Framework Search Paths”中添加Realm.framework的上级目录;

4、在 iOS、watchOS 或者 tvOS 项目中使用 了Realm,在”Build Phases”中,创建一个新的”Run Script Phase”,将脚本复制到文本框中用来绕过APP商店提交的bug,这在打包通用设备的二进制发布版本时是必须的

bash "${BUILT_PRODUCTS_DIR}/${FRAMEWORKS_FOLDER_PATH}/Realm.framework/strip-frameworks.sh"

8.2 Realm的重要概念

RLMRealm:RLMRealm是框架的核心,如同Core Data的托管对象上下文

RLMObject:数据模型,创建自定义的数据模型需要继承自RLMObject

Relationships:在数据模型中声明一个RLMObject类型的属性,就可以创建一个对象关系

Write Transactions:写操作事物,数据库中的创建、删除对象等,都应该在事物中完成

Queries:查询数据库中的信息,可以使用断言、复合查询等进行数据查询

RLMResults:查询结果集,其中包含一系列的RLMObject对象,RLMResults和NSArray类似,我们可以用下标语法来对其进行访问

8.3 Realm数据库的使用

在实际开发中,通常都需要对Core Data、SQLite3、FMDB分装一个单例类。
但是Realm数据库通过[RLMRealm defaultRealm]就可以获取到当前realm对象的一个实例,它本身就是一个单利,所以我们每次在子线程里面不要再去读取我们自己封装持有的realm实例了,直接调用系统的这个方法即可。需要注意的是同一个Realm对象是不支持跨线程操作realm数据库的,在Realm中每个线程都拥有Realm的一个快照,可以同时有任意数目的线程访问同一个 Realm 文件,线程之间不会产生影响

8.3.1 创建数据库

在"- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions"方法中创建数据库

    NSString *documentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject;
    NSString *dbFolder = [documentPath stringByAppendingPathComponent:@"RealmDB"];
    if (![[NSFileManager defaultManager] fileExistsAtPath:dbFolder]) {
        [[NSFileManager defaultManager] createDirectoryAtPath:dbFolder withIntermediateDirectories:YES attributes:nil error:nil];
    }
    NSString *filePath = [dbFolder stringByAppendingPathComponent:@"db.realm"];
    RLMRealmConfiguration *config = [RLMRealmConfiguration defaultConfiguration];
    //路径
    config.fileURL = [NSURL URLWithString:filePath];
    //是否只读
    config.readOnly = NO;
    //当前版本
    config.schemaVersion = 4;
    [RLMRealmConfiguration setDefaultConfiguration:config];

8.3.2 创建数据模型

Realm中创建自定义的数据模型需要继承自RLMObject,所以可以创建一个名为HJRealmBaseModel自定义类先继承自RLMObject

#import 
#import 

NS_ASSUME_NONNULL_BEGIN

@interface HJRealmBaseModel : RLMObject

@end

NS_ASSUME_NONNULL_END
#import "HJRealmBaseModel.h"

@implementation HJRealmBaseModel

@end

创建一个HJRealmPersonModel类和HJRealmCarModel类继承自HJRealmBaseModel,
HJRealmPersonModel对于HJRealmCarModel的关系为一对多,由于Realm数据库不支持集合类型,比如说NSArray,NSMutableArray,NSDictionary,NSMutableDictionary,NSSet,NSMutableSet,所以集合类型的属性是不能直接存储到数据库的。当然Realm里面是有集合的,就是RLMArray,这里面装的都是RLMObject。
解决这个问题,如果是model,就先自己接收一下,然后将数据转换成RLMObject的model,在存储到RLMArray里,然后使用"ignoredProperties"方法忽略掉不能存储的属性

HJRealmCarModel.h

#import "HJRealmBaseModel.h"

NS_ASSUME_NONNULL_BEGIN

@interface HJRealmCarModel : HJRealmBaseModel

@property (nonatomic, assign) NSInteger carId;
@property (nonatomic, copy) NSString *carName;

@end
//RLM_ARRAY_TYPE宏创建了一个协议,从而允许 RLMArray语法的使用
RLM_ARRAY_TYPE(HJRealmCarModel)

NS_ASSUME_NONNULL_END

HJRealmCarModel.m


#import "HJRealmCarModel.h"

@implementation HJRealmCarModel

/**
 主键

 @return return value description
 */
+ (NSString *)primaryKey {
    return @"carId";
}


/**
 属性值不能为空

 @return return value description
 */
+ (NSArray *)requiredProperties {
    return @[@"carId"];
}

/**
 忽略属性

 @return return value description
 */
+ (NSArray *)ignoredProperties {
    return @[];
}

@end

HJRealmPersonModel.h

#import "HJRealmBaseModel.h"
#import "HJRealmCarModel.h"

NS_ASSUME_NONNULL_BEGIN

@interface HJRealmPersonModel : HJRealmBaseModel

@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) NSInteger userId;
@property (nonatomic, assign) NSInteger age;
@property (nonatomic, strong) NSString *address;
@property (nonatomic, strong) RLMArray *cars;

@end
NS_ASSUME_NONNULL_END

HJRealmPersonModel.m

#import "HJRealmPersonModel.h"

@implementation HJRealmPersonModel

+ (NSString *)primaryKey {
    return @"userId";
}

+ (NSArray *)requiredProperties {
    return @[@"userId"];
}

+ (NSArray *)ignoredProperties {
    return @[];
}

@end

8.3.3 数据的增删改查示例

Realm数据库的操作都应该在事物当中进行

#pragma mark - Realm数据操作
/**
 增加记录
 
 @param sender sender description
 */
- (IBAction)realmInsertButtonDidClicked:(UIButton *)sender {
    RLMArray *car;
    HJRealmCarModel *carModel = [HJRealmCarModel new];
    carModel.carId = 111111;
    [car addObject:carModel];
    HJRealmPersonModel *model = [HJRealmPersonModel new];
    model.userId = 1;
    model.cars = car;
    [[RLMRealm defaultRealm] transactionWithBlock:^{
        [[RLMRealm defaultRealm] addOrUpdateObject:model];
    }];
}
/**
 删除记录
 
 @param sender sender description
 */
- (IBAction)realmDeleteButtonDidClicked:(UIButton *)sender {
    [[RLMRealm defaultRealm] transactionWithBlock:^{
        RLMResults *results = [HJRealmPersonModel objectsWhere:@"userId = 1"];
        NSLog(@"%@",results);
        [[RLMRealm defaultRealm] deleteObjects:results];
    }];
    
}
/**
 修改记录
 
 @param sender sender description
 */
- (IBAction)realmUpdateButtonDidClicked:(UIButton *)sender {
    HJRealmPersonModel *model = [HJRealmPersonModel new];
    model.userId = 1;
    model.name = @"小星星";
    [[RLMRealm defaultRealm] transactionWithBlock:^{
        [[RLMRealm defaultRealm] addOrUpdateObject:model];
    }];
}
/**
 查询记录
 
 @param sender sender description
 */
- (IBAction)realmSelectButtonDidClicked:(UIButton *)sender {
    [[RLMRealm defaultRealm] transactionWithBlock:^{
        RLMResults *results = [HJRealmPersonModel objectsWhere:@"userId = 1"];
        NSLog(@"%@",results.firstObject);
    }];
}

总结
经过上面的分析
plist文件主要用于不经常修改、数据量小的数据
偏好设置主要用于检查版本是否更新、是否启动引导页、自动登录、版本号等程序设置归
档解归档主要是归档之后的文件时加密的,用于一些数据量小的数据,数据库操作比较笨拙
沙盒路径可以提高程序的体验度,为用户节约数据流量,主要在用户阅读书籍、听音乐、看视频等
Core Data提供了对象关系的映射功能,使得能够将OC对象转换成数据,将数据库中的数据还原成OC对象,在转换的过程中不需要编写任何的SQL语句
SQLite3是轻量级的数据库,占用资源很少,需要大量的SQL语句
FMDB是对SQLite3的进一步封装,减去了C语言风格,更加的面向对象,同样需要大量的SQL语句
Realm本质上也是一个嵌入式数据库,更加的轻量级,支持跨平台,没有Core Data与SQLite冗余、复杂的知识和代码,更加的面向对象,学习成本更小

你可能感兴趣的:(iOS 数据持久化详解)