iOS下的dao層實現代碼

什麼是dao層

DAO (Data Access Object) 數據訪問對象是一個面向對象的接口. 直接操作數據庫, 針對數據的增添,刪除,修改,查找,具體為業務邏輯層或表示層提供數據服務.

一個dao的例子

- (void)saveRemind:(RemindEntity *)remind; // 保存一個提醒
- (void)deleteRemindWithWhere:(NSString *)where; // 刪除一個提醒
- (RemindEntity *) loadRemindWithRemindID:(NSString *)rid; // 讀取一個提醒
- (void)deleteRemindWithRemindID:(NSString *)rid; // 刪除一個提醒
- (void)deleteRemindWithWeihuaId:(NSString *)weihuaId rcdId:(int)rcdId; // 刪除一個聯系人或者微話好友的提醒
- (NSArray *)searchRemindWithWhere:(NSString *)where
                            order:(NSString *)order
                            limit:(NSString *)limit; // 查找提醒
- (NSInteger)remindCountWithWhere:(NSString *)where; // 返回提醒數量
- (NSArray *)allArrivalReminds; // 返回所有未過期, 下次開始時間小於現在時間的提醒
- (NSArray *)allNonOverdueReminds; // 返回所有未過期的提醒
+ (void) setupDB; // 初始化數據庫

內部實現是用fmdb,得寫大量的sql.如果我們有多個實體類, 就得寫多個dao.

范化的dao

下面我們來看一個范化的dao, 就不用為每個實體專門寫sql了,具體使用的時候可以繼承這個類或者寫個工廠類.

@protocol XYBaseDaoEntityProtocol 

@required
// 返回表名
+ (NSString *)getTableName;

// 返回主鍵
+ (NSString *)getPrimaryKey;

@end


// 范化的本地dao類
@interface XYBaseDao : NSObject

@property (nonatomic, weak, readonly) Class entityClass;

+ (instancetype)daoWithEntityClass:(Class)aClass;

- (NSError *)saveEntity:(id)entity;
- (NSError *)saveEntityWithArray:(NSArray *)array;

- (id)loadEntityWithKey:(NSString *)key;
- (NSArray *)loadEntityWithWhere:(NSString *)where;

- (NSInteger)countWithWhere:(NSString *)where;

- (NSError *)deleteEntityWithKey:(NSString *)key;
- (NSError *)deleteEntityWithWhere:(NSString *)where;

- (void)deleteAllEntity;

@end

這個dao是基於LKDBHelper的, 把實體對象的類當初始化參數傳進去.

+ (instancetype)daoWithEntityClass:(Class)aClass
{
    XYBaseDao *dao = [[[self class] alloc] initWithEntityClass:aClass];

    return dao;
}

- (instancetype)initWithEntityClass:(Class)aClass
{
    self = [super init];
    if (self)
    {
        _entityClass = aClass;
        _globalHelper = [LKDBHelper getUsingLKDBHelper];
        // 創建表
        [_globalHelper createTableWithModelClass:[_entityClass class]];
    }
    return self;
}

- (NSError *)saveEntity:(id)entity
{
    if (entity == nil)
        return [NSError errorWithDomain:[NSString stringWithFormat:@"[save error] :%@", entity] code:XYBaseDao_error_code userInfo:nil];

    LKDBHelper *globalHelper = [LKDBHelper getUsingLKDBHelper];

    if (![globalHelper insertToDB:entity])
    {
        return [NSError errorWithDomain:[NSString stringWithFormat:@"[save error] :%@", entity] code:XYBaseDao_error_code userInfo:nil];
    }

    return nil;
}

- (NSError *)saveEntityWithArray:(NSArray *)array
{
    if (array == nil || array.count == 0)
        return [NSError errorWithDomain:[NSString stringWithFormat:@"[save error] :%@", array] code:XYBaseDao_error_code userInfo:nil];

    NSMutableString *str = [NSMutableString stringWithFormat:@"[save error] :"];
    NSInteger length = str.length;

    __weak __typeof(XYBaseDao *) weakSelf = self;

    // 事務  transaction
    [_globalHelper executeDB:^(FMDatabase *db) {
        [db beginTransaction];
        for (NSObject *entity in array)
        {
            if (![weakSelf.globalHelper insertToDB:entity])
            {
                [str stringByAppendingFormat:@"%@ ", entity];
            }
        }
        [db commit];
    }];

    if (str.length > length)
    {
        return [NSError errorWithDomain:str code:XYBaseDao_error_code userInfo:nil];
    }

    return nil;
}

- (id)loadEntityWithKey:(NSString *)key
{
    if (key.length == 0)
        return nil;

    id object = [[_entityClass alloc] init];

    NSString *where = nil;

    if ([key isKindOfClass:[NSString class]])
    {
        where = [NSString stringWithFormat:@"%@ = '%@'", [_entityClass getPrimaryKey], key];
    }
    else if ([key isKindOfClass:[NSNumber class]])
    {
        where = [NSString stringWithFormat:@"%@ = %@", [_entityClass getPrimaryKey], key];
    }
    else if (1)
    {
#pragma mark- todo  多主鍵種類判斷
        where = @"";
    }

    object = [_entityClass searchSingleWithWhere:where orderBy:nil];

    return object;
}

- (NSArray *)loadEntityWithWhere:(NSString *)where
{
    if (where.length == 0)
        return nil;

    NSArray *array = [_entityClass searchWithWhere:where orderBy:nil offset:0 count:XYBaseDao_load_maxCount];

    return array;
}

- (NSInteger)countWithWhere:(NSString *)where
{
    return [_entityClass rowCountWithWhere:where];
}

- (NSError *)deleteEntityWithKey:(NSString *)key
{
    id object = [[_entityClass alloc] init];
    [object setValue:key forKey:[_entityClass getPrimaryKey]];

    if (![object deleteToDB])
    {
        return  [NSError errorWithDomain:[NSString stringWithFormat:@"[delete error] : %@ %@", _entityClass, key] code:XYBaseDao_error_code userInfo:nil];
    }

    return nil;
}

- (NSError *)deleteEntityWithWhere:(NSString *)where
{
    if (![_entityClass deleteWithWhere:where])
    {
        return  [NSError errorWithDomain:[NSString stringWithFormat:@"[delete error] : %@ %@", _entityClass, where] code:XYBaseDao_error_code userInfo:nil];
    }

    return nil;
}

- (void)deleteAllEntity
{
    [LKDBHelper clearTableData:[_entityClass class]];
}

最後是demo

- (void)clickTestDao:(id)sender
{
    XYBaseDao *dao = [XYBaseDao daoWithEntityClass:[CarEntity class]];
    [dao deleteAllEntity];

    CarEntity *car = [[CarEntity alloc] init];
    car.name = @"a";
    car.brand = @"科魯茲";
    car.time = 1;

    [dao saveEntity:car];

    CarEntity *car2 = [[CarEntity alloc] init];
    car2.name = @"b";
    car2.brand = @"科魯茲";
    car2.time = 1;

    CarEntity *car3 = [[CarEntity alloc] init];
    car3.name = @"c";
    car3.brand = @"福克斯";
    car3.time = 1;

    CarEntity *car5 = [[CarEntity alloc] init];
    car5.name = @"d";
    car5.brand = @"高爾夫";
    car5.time = 1;

    NSArray *array = @[car2, car3, car5];

    [dao saveEntityWithArray:array];

    CarEntity *car4 = [dao loadEntityWithKey:@"c"];
    NSLog(@"%@", car4);

    NSArray *array2 = [dao loadEntityWithWhere:@"brand = '科魯茲'"];
    NSLog(@"%@", array2);

    NSInteger count = [dao countWithWhere:nil];
    NSLog(@"%d", count);

    [dao deleteEntityWithKey:@"c"];
    [dao deleteEntityWithKey:@"brand = '科魯茲'"];
}