FMDB介绍
FMDB是iOS平台的SQLite数据库框架
FMDB以OC的方式封装了SQLite的C语言API
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
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基本使用
FMDB GitHub链接: https://github.com/ccgus/fmdb
1.导入FMDB文件
2.导入系统依赖库sqlite3.0.tbd
创建数据库并打开
/*
1. 如果该路径下已经存在该数据库，直接获取该数据库;
2. 如果不存在就创建一个新的数据库;
3. 如果传@""，会在临时目录创建一个空的数据库，当数据库关闭时，数据库文件也被删除;
4. 如果传nil，会在内存中临时创建一个空的数据库，当数据库关闭时，数据库文件也被删除;
*/
+ (FMDatabase *)databaseWithPath:(NSString *)filePath;
// 1.获得数据库文件的路径
NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *filename = [doc stringByAppendingPathComponent:@"my.sqlite"];
// 2.得到数据库
FMDatabase* db = [FMDatabase databaseWithPath:filename];
// 3.打开数据库
if ([db open]) {
NSLog(@"打开数据库成功");
}else {
NSLog(@"打开数据库失败");
}
执行更新
在FMDB中，除查询以外的所有操作，都称为“更新”
create、drop、insert、update、delete等
使用executeUpdate:方法执行更新
/* 执行更新的SQL语句，字符串里面的"?"，依次用后面的参数替代，必须是对象，不能是int等基本类型 */
- (BOOL)executeUpdate:(NSString *)sql,... ;
/* 执行更新的SQL语句，可以使用字符串的格式化进行构建SQL语句 */
- (BOOL)executeUpdateWithFormat:(NSString*)format,... ;
/* 执行更新的SQL语句，字符串中有"?"，依次用arguments的元素替代 */
- (BOOL)executeUpdate:(NSString*)sql withArgumentsInArray:(NSArray *)arguments;
/* 1. 直接使用完整的SQL更新语句 */
[database executeUpdate:@"insert into mytable(num,name,sex) values(0,'liuting','m');"];
NSString *sql = @"insert into mytable(num,name,sex) values(?,?,?);";
/* 2. 使用不完整的SQL更新语句，里面含有待定字符串"?"，需要后面的参数进行替代 */
[database executeUpdate:sql,@0,@"liuting",@"m"];
/* 3. 使用不完整的SQL更新语句，里面含有待定字符串"?"，需要数组参数里面的参数进行替代 */
[database executeUpdate:sql
withArgumentsInArray:@[@0,@"liuting",@"m"]];
/* 4. SQL语句字符串可以使用字符串格式化，这种我们应该比较熟悉 */
[database executeUpdateWithFormat:@"insert into mytable(num,name,sex) values(%d,%@,%@);",0,@"liuting","m"];
执行查询
- (FMResultSet *)executeQuery:(NSString*)sql, ...
- (FMResultSet *)executeQueryWithFormat:(NSString*)format, ...
- (FMResultSet *)executeQuery:(NSString *)sql withArgumentsInArray:(NSArray *)arguments
- 处理结果FMResultSet的方法
/* 获取下一个记录 */
- (BOOL)next;
/* 获取记录有多少列 */
- (int)columnCount;
/* 通过列名得到列序号，通过列序号得到列名 */
- (int)columnIndexForName:(NSString *)columnName;
- (NSString *)columnNameForIndex:(int)columnIdx;
/* 获取存储的整形值 */
- (int)intForColumn:(NSString *)columnName;
- (int)intForColumnIndex:(int)columnIdx;
/* 获取存储的长整形值 */
- (long)longForColumn:(NSString *)columnName;
- (long)longForColumnIndex:(int)columnIdx;
/* 获取存储的布尔值 */
- (BOOL)boolForColumn:(NSString *)columnName;
- (BOOL)boolForColumnIndex:(int)columnIdx;
/* 获取存储的浮点值 */
- (double)doubleForColumn:(NSString *)columnName;
- (double)doubleForColumnIndex:(int)columnIdx;
/* 获取存储的字符串 */
- (NSString *)stringForColumn:(NSString *)columnName;
- (NSString *)stringForColumnIndex:(int)columnIdx;
/* 获取存储的日期数据 */
- (NSDate *)dateForColumn:(NSString *)columnName;
- (NSDate *)dateForColumnIndex:(int)columnIdx;
/* 获取存储的二进制数据 */
- (NSData *)dataForColumn:(NSString *)columnName;
- (NSData *)dataForColumnIndex:(int)columnIdx;
/* 获取存储的UTF8格式的C语言字符串 */
- (const unsigned cahr *)UTF8StringForColumnName:(NSString *)columnName;
- (const unsigned cahr *)UTF8StringForColumnIndex:(int)columnIdx;
/* 获取存储的对象，只能是NSNumber、NSString、NSData、NSNull */
- (id)objectForColumnName:(NSString *)columnName;
- (id)objectForColumnIndex:(int)columnIdx;
- 如何使用
+ (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;
}
- 关闭数据库
[_db close];
FMDabaseQueue的使用
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
创建FMDabaseQueue
NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"shops.sqlite"];
FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath:path];
使用FMDabaseQueue
[queue inDatabase:^(FMDatabase*db) {
//插入记录到表中
NSString *sqlStr = @"CREATE TABLE IF NOT EXISTS t_shop (id integer PRIMARY KEY, name text NOT NULL, price real);"；
BOOL result = [db executeUpdate:sqlStr];
if (!result) {
NSLog(@"error when insert into database table");
[db close];
}
}];
事务
事务，是指作为单个逻辑工作单元执行的一系列操作，要么完整地执行，要么完全地不执行。
比如你要更新数据库的大量数据，我们需要确保所有的数据更新成功才行，如果在更新期间出现错误，就不好办了。如果我们不使用事务，我们的更新操作直接对每个记录生效，万一遇到更新错误，已经更新的数据怎么办？难道我们要一个一个去找出来修改回来吗？事务就是解决这种情况的，只有所有的数据更新正确才成功，如果有一条更新错误，那么所有的数据都回到解放前，变为没有更新状态。
来个demo更好理解吧
- FMDatabase使用事务
//事务
-(void)startTransaction {
// 开启事务
[self.database beginTransaction];
BOOL isRollBack = NO;
@try {
for (int i = 0; i<100; i++) {
NSNumber *num = @(i+1);
NSString *name = [[NSString alloc] initWithFormat:@"student_%d",i];
NSString *sql = @"insert into mytable(num,name) values(?,?);";
BOOL result = [database executeUpdate:sql,num,name,sex];
if ( !result ) {
NSLog(@"插入失败！");
return;
}
}
}
@catch (NSException *exception) {
isRollBack = YES;
// 事务回退
[self.database rollback];
}
@finally {
if (!isRollBack) {
//事务提交
[self.database commit];
}
}
}
- FMDatabaseQueue使用事务
//多线程事务
- (void)transactionByQueue {
//开启事务
[self.queue inTransaction:^(FMDatabase *db, BOOL *rollback) {
for (int i = 0; i<500; i++) {
NSNumber *num = @(i+1);
NSString *name = [[NSString alloc] initWithFormat:@"student_%d",i];
NSString *sex = (i%2==0)?@"f":@"m";
NSString *sql = @"insert into mytable(num,name,sex) values(?,?,?);";
BOOL result = [db executeUpdate:sql,num,name,sex];
if ( !result ) {
//当最后*rollback的值为YES的时候，事务回退，如果最后*rollback为NO，事务提交
*rollback = YES;
return;
}
}
}];
}
demo展示
@interface ViewController ()
@property (nonatomic, strong) FMDatabase *db;
@end
@implementation ViewController
@synthesize db;
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
// 1.获得数据库文件的路径
NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *filename = [doc stringByAppendingPathComponent:@"operDB.sqlite"];
// 2.得到数据库
db = [FMDatabase databaseWithPath:filename];
}
- (IBAction)openDB:(id)sender {
// 3.打开数据库
if ([db open]) {
NSLog(@"打开operDB成功");
}else {
NSLog(@"打开operDB失败");
}
}
- (IBAction)createShopCarTable:(id)sender {
// 4.创表
if ([db open]) {
BOOL result = [db executeUpdate:@"CREATE TABLE IF NOT EXISTS shopCar (dbid integer PRIMARY KEY AUTOINCREMENT, specId integer NOT NULL, shopNum integer NOT NULL default 1, shopInfo TEXT NOT NULL);"];
if (result) {
NSLog(@"成功创表");
} else {
NSLog(@"创表失败");
}
[db close];
}
}
- (IBAction)insertData:(id)sender {
if ([db open]) {
for (int i = 0; i < 5; i++) {
NSDictionary *dict = @{@"shopId":@(i+1),@"shopName":@"欧阳公仔",@"shopPrice":@(55.9 + i)};
NSString *shopInfo = [dict mj_JSONString];
NSString *insertSql1= [NSString stringWithFormat:@"INSERT INTO shopCar (specId, shopNum, shopInfo) VALUES (%d, %d, '%@')", i+2, i+3, shopInfo];
BOOL res = [db executeUpdate:insertSql1];
if (res) {
NSLog(@"数据插入表成功");
} else {
NSLog(@"数据插入表失败");
}
}
[db close];
}
}
- (IBAction)selectAllData:(id)sender {
if ([db open]) {
NSString * sql = @"SELECT * FROM shopCar";
FMResultSet * rs = [db executeQuery:sql];
while ([rs next]) {
int dbId = [rs intForColumn:@"dbid"];
int specId = [rs intForColumn:@"specId"];
int shopNum = [rs intForColumn:@"shopNum"];
NSString * shopInfo = [rs stringForColumn:@"shopInfo"];
NSLog(@"dbId = %d, specId = %d, shopNum = %d shopInfo = %@", dbId, specId, shopNum, shopInfo);
}
[db close];
}
}
- (IBAction)selectDbidData:(id)sender {
if ([db open]) {
NSString * sql = @"SELECT * FROM shopCar WHERE dbid = '3'";
FMResultSet * rs = [db executeQuery:sql];
while ([rs next]) {
int dbId = [rs intForColumn:@"dbid"];
int specId = [rs intForColumn:@"specId"];
int shopNum = [rs intForColumn:@"shopNum"];
NSString * shopInfo = [rs stringForColumn:@"shopInfo"];
NSLog(@"dbId = %d, specId = %d, shopNum = %d shopInfo = %@", dbId, specId, shopNum, shopInfo);
}
[db close];
}
}
- (IBAction)updataDbidData:(id)sender {
if ([db open]) {
NSString *updateSql = [NSString stringWithFormat:@"update shopCar set shopNum = '88' where dbid ='3'"];
BOOL res = [db executeUpdate:updateSql];
if (res) {
NSLog(@"修改数据成功");
} else {
NSLog(@"修改数据失败");
}
[db close];
}
}
- (IBAction)deleteDbidData:(id)sender {
if ([db open]) {
NSString *updateSql = [NSString stringWithFormat:@"DELETE FROM shopCar WHERE dbid = '3'"];
BOOL res = [db executeUpdate:updateSql];
if (res) {
NSLog(@"删除指定数据成功");
} else {
NSLog(@"删除指定数据失败");
}
[db close];
}
}
- (IBAction)deleteAllData:(id)sender {
if ([db open]) {
//清空数据表并将自增字段清零
NSString *deleteSql = @"DELETE FROM shopCar";
[db executeUpdate:@"UPDATE sqlite_sequence set seq = 0 where name = 'shopCar'"];
BOOL res = [db executeUpdate:deleteSql];
if (res) {
NSLog(@"清空shopCar表数据成功");
} else {
NSLog(@"清空shopCar表数据失败");
}
[db close];
}
}
- (IBAction)deleteShopCarTable:(id)sender {
if ([db open]) {
NSString *deleteSql = @"DROP TABLE shopCar";
BOOL res = [db executeUpdate:deleteSql];
if (res) {
NSLog(@"删除shopCar表成功");
} else {
NSLog(@"删除shopCar表失败");
}
[db close];
}
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end