IOS FMDB-白红宇

IOS FMDB

阅读量：4962 次

发布时间：2019-06-12

本文共 5006 字，大约阅读时间需要 16 分钟。

● 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

● 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

● 为了保证线程安全,FMDB提供方便快捷的FMDatabaseQueue类 ● FMDatabaseQueue的创建

FMDatabaseQueue *queue = [FMDatabaseQueuedatabaseQueueWithPath:path];

●

简单使用

[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 HMShopToolstatic 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

View Code

#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];    }}

View Code