iOS下的dao层实现代码

iOS下的dao层实现代码

什么是dao层

DAO (Data Access Object) 数据访问对象是一个面向对象的接口. 直接操作数据库, 针对数据的增添,删除,修改,查找,具体为业务逻辑层或表示层提供数据服务.

一个dao的例子

- (void)saveRemind:(RemindEntity *)remind; // 保存一个提醒- (void)deleteRemindWithWhere:(NSString *)where; // 删除一个提醒- (RemindEntity *) loadRemindWithRemindID:(NSString *)rid; // 读取一个提醒- (void)deleteRemindWithRemindID:(NSString *)rid; // 删除一个提醒- (void)deleteRemindWithWeihuaId:(NSString *)weihuaId rcdId:(int)rcdId; // 删除一个联系人或者微话好友的提醒- (NSArray *)searchRemindWithWhere:(NSString *)where                            order:(NSString *)order                            limit:(NSString *)limit; // 查找提醒- (NSInteger)remindCountWithWhere:(NSString *)where; // 返回提醒数量- (NSArray *)allArrivalReminds; // 返回所有未过期, 下次开始时间小于现在时间的提醒- (NSArray *)allNonOverdueReminds; // 返回所有未过期的提醒+ (void) setupDB; // 初始化数据库

内部实现是用fmdb,得写大量的sql.如果我们有多个实体类, 就得写多个dao.

范化的dao

下面我们来看一个范化的dao, 就不用为每个实体专门写sql了,具体使用的时候可以继承这个类或者写个工厂类.

@protocol XYBaseDaoEntityProtocol <NSObject>@required// 返回表名+ (NSString *)getTableName;// 返回主键+ (NSString *)getPrimaryKey;@end// 范化的本地dao类@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

这个dao是基于LKDBHelper的, 把实体对象的类当初始化参数传进去.

+ (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];        // 创建表        [_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;    // 事务  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  多主键种类判断        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]];}

最后是demo

- (void)clickTestDao:(id)sender{    XYBaseDao *dao = [XYBaseDao daoWithEntityClass:[CarEntity class]];    [dao deleteAllEntity];    CarEntity *car = [[CarEntity alloc] init];    car.name = @"a";    car.brand = @"科鲁兹";    car.time = 1;    [dao saveEntity:car];    CarEntity *car2 = [[CarEntity alloc] init];    car2.name = @"b";    car2.brand = @"科鲁兹";    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 = @"高尔夫";    car5.time = 1;    NSArray *array = @[car2, car3, car5];    [dao saveEntityWithArray:array];    CarEntity *car4 = [dao loadEntityWithKey:@"c"];    NSLog(@"%@", car4);    NSArray *array2 = [dao loadEntityWithWhere:@"brand = '科鲁兹'"];    NSLog(@"%@", array2);    NSInteger count = [dao countWithWhere:nil];    NSLog(@"%d", count);    [dao deleteEntityWithKey:@"c"];    [dao deleteEntityWithKey:@"brand = '科鲁兹'"];}