● FMDB的优点
● 使用起来更加面向对象,省去了很多麻烦、冗余的C语言代码
● 对比苹果自带的Core Data框架,更加轻量级和灵活
● 提供了多线程安全的数据库操作方法,有效地防止数据混乱
● FMDB的github地址
● https://github.com/ccgus/fmdb
● FMDB有三个主要的类
● FMDatabase
• 一个FMDatabase对象就代表一个单独的SQLite数据库 • 用来执行SQL语句
• 一个FMDatabase对象就代表一个单独的SQLite数据库 • 用来执行SQL语句
● FMResultSet
• 使用FMDatabase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,它是线程安全的
打开数据库
● 通过指定SQLite数据库文件路径来创建FMDatabase对象 FMDatabase *db = [FMDatabase databaseWithPath:path]; if (![db open]) {
NSLog(@"数据库打开失败!"); }
● 文件路径有三种情况
● 具体文件路径
• 如果不存在会自动创建
● 空字符串@""
• 会在临时目录创建一个空的数据库
• 当FMDatabase连接关闭时,数据库文件也被删除
● nil
• 会创建一个内存中临时数据库,当FMDatabase连接关闭时,数据库会被销毁
执行查询
● 查询方法
● -(FMResultSet*)executeQuery:(NSString*)sql,...
● -(FMResultSet*)executeQueryWithFormat:(NSString*)format,...
● -(FMResultSet*)executeQuery:(NSString*)sql withArgumentsInArray:(NSArray *)arguments
● 示例
// 查询数据
FMResultSet *rs = [db executeQuery:@"SELECT * FROM t_student"];
// 遍历结果集
while ([rs next]) {
NSString *name = [rs stringForColumn:@"name"];
int age = [rs intForColumn:@"age"];
double score = [rs doubleForColumn:@"score"];
}
FMDatabaseQueue
● FMDatabase这个类是线程不安全的,如果在多个线程中同时使用一 个FMDatabase实例,会造成数据混乱等问题
View Code
View Code
● 为了保证线程安全,FMDB提供方便快捷的FMDatabaseQueue类 ● FMDatabaseQueue的创建
FMDatabaseQueue *queue = [FMDatabaseQueue
databaseQueueWithPath:path];
● 简单使用
[queue inDatabase:^(FMDatabase *db) {
[queue inDatabase:^(FMDatabase *db) {
[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jack"];
[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Rose"];
[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jim"];
FMResultSet *rs = [db executeQuery:@"select * from t_student"];
while ([rs next]) {
// ...
} }];
●使用事务
[queue inTransaction:^(FMDatabase *db, BOOL *rollback) {
[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jack"];
[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Rose"];
[db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jim"];
FMResultSet *rs = [db executeQuery:@"select * from t_student"];
while ([rs next]) {
// ...
} }];
● 事务回滚 *rollback = YES;
1.打开数据库
2.创建表
3.查询表
#import "HMShopTool.h" #import "FMDB.h" #import "HMShop.h" @implementation HMShopTool static FMDatabase *_db; + (void)initialize { // 1.打开数据库 NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"shops.sqlite"]; _db = [FMDatabase databaseWithPath:path]; [_db open]; // 2.创表 [_db executeUpdate:@"CREATE TABLE IF NOT EXISTS t_shop (id integer PRIMARY KEY, name text NOT NULL, price real);"]; } + (void)addShop:(HMShop *)shop { [_db executeUpdateWithFormat:@"INSERT INTO t_shop(name, price) VALUES (%@, %f);", shop.name, shop.price]; } + (NSArray *)shops {// 得到结果集 FMResultSet *set = [_db executeQuery:@"SELECT * FROM t_shop;"]; // 不断往下取数据 NSMutableArray *shops = [NSMutableArray array]; while (set.next) { // 获得当前所指向的数据 HMShop *shop = [[HMShop alloc] init]; shop.name = [set stringForColumn:@"name"]; shop.price = [set doubleForColumn:@"price"]; [shops addObject:shop]; } return shops; } @end
#import "HMViewController.h" #import "FMDB.h" #import "HMShop.h" #import "HMShopTool.h" @interface HMViewController () //@property (nonatomic, strong) FMDatabase *db; @end @implementation HMViewController - (void)viewDidLoad { [super viewDidLoad]; // 1.打开数据库 NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"shops.sqlite"]; self.db = [FMDatabase databaseWithPath:path]; [self.db open]; // // // 2.创表 [self.db executeUpdate:@"CREATE TABLE IF NOT EXISTS t_shop (id integer PRIMARY KEY, name text NOT NULL, price real);"]; // executeQuery:查询数据 [self.db executeQuery:<#(NSString *), ...#>]; // executeUpdate:除查询数据以外的其他操作 [self.db executeUpdate:<#(NSString *), ...#>]; } - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { // for (int i = 0; i<100; i++) { // HMShop *shop = [[HMShop alloc] init]; // shop.name = [NSString stringWithFormat:@"枕头--%d", i]; // shop.price = arc4random() % 200; // [HMShopTool addShop:shop]; // } NSArray *shops = [HMShopTool shops]; for (HMShop *shop in shops) { NSLog(@"%@ %f", shop.name, shop.price); } [self.db executeUpdate:@"DELETE FROM t_shop WHERE price < 800;"]; [self query]; } - (void)query { // 得到结果集 FMResultSet *set = [self.db executeQuery:@"SELECT * FROM t_shop;"]; // 不断往下取数据 while (set.next) { // 获得当前所指向的数据 NSString *name = [set stringForColumn:@"name"]; double price = [set doubleForColumn:@"price"]; NSLog(@"%@ %f", name, price); } } - (void)insert { for (int i = 0; i<100; i++) { NSString *name = [NSString stringWithFormat:@"手机-%d", i]; #warning 这里的字符串不用再加上'' [self.db executeUpdateWithFormat:@"INSERT INTO t_shop(name, price) VALUES (%@, %d);", name, arc4random()%1000]; } }