iOS下FMDB的多线程操作（一）
iOS中一些时间比较长的操作都应该放在子线程中，以避免UI的卡顿。而sqlite 是非线程安全的，故在多线程中不能共用同一个数据库连接，否则会导致EXC_BAD_ACCESS。所以我们可以在子线程中创建一个新的db连接（新建一个db对象），然后再操作数据库。
如果选择FMDB，除了以上所说的方式外，还可以利用FMDatabaseQueue来解决多线程问题。
关于FMDB的使用网上教程比较多，内容基本都是与唐巧的这篇http://www.devtang.com/blog/2012/04/22/use-fmdb/差不多
这里记录一下多线程下的使用。
方式一：采用每次新建db的方式
db路径我是写了一个方法
+ (NSString *)getDBPath
{
NSString* docsdir = [NSSearchPathForDirectoriesInDomains( NSDocumentDirectory, NSUserDomainMask,YES) lastObject];
NSFileManager *filemanage = [NSFileManager defaultManager];
docsdir = [docsdir stringByAppendingPathComponent:@"FMDBDemo"];
BOOL isDir;
BOOL exit =[filemanage fileExistsAtPath:docsdir isDirectory:&isDir];
if (!exit || !isDir) {
[filemanage createDirectoryAtPath:docsdir withIntermediateDirectories:YES attributes:nil error:nil];
}
NSString *dbpath = [docsdir stringByAppendingPathComponent:@"myDB.sqlite"];
return dbpath;
}
1、创建数据库表
/** 创建表 */
+ (BOOL)createUserTableByDB
{
FMDatabase *db = [FMDatabase databaseWithPath:[self getDBPath]];
if (![db open]) {
NSLog(@"数据库打开失败!");
return NO;
}
NSString *sql = @"CREATE TABLE IF NOT EXISTS User(ID INTEGER PRIMARY KEY, name TEXT, age INTEGER, ID_No TEXT);";
BOOL res = [db executeUpdate:sql];
if (res) {
NSLog(@"创建表格成功");
}else {
NSLog(@"创建表格失败");
}
return res;
}
2、插入数据
插入数据，我分了两种情形，一种是单条插入，一种是利用事务（利用事务插入多条时，时间会快很多，而且有任何一条插入失败，则不会提交到数据库）
/** 保存单个对象 */
- (BOOL)saveByDB
{
FMDatabase *db = [FMDatabase databaseWithPath:[User getDBPath]];
if (![db open]) {
NSLog(@"数据库打开失败!");
return NO;
}
NSString *sql = [NSString stringWithFormat:@"INSERT INTO User(name, age, ID_No) VALUES ('%@', '%d', '%@');", self.name, self.age, self.ID_no];
BOOL res = [db executeUpdate:sql];
[db close];
if (res) {
NSLog(@"插入数据成功");
}else {
NSLog(@"插入数据失败");
}
return res;
}
/** 批量保存用户对象 */
+ (BOOL)saveObjectsByDB:(NSArray *)array
{
FMDatabase *db = [FMDatabase databaseWithPath:[self getDBPath]];
if (![db open]) {
NSLog(@"数据库打开失败!");
return NO;
}
[db beginTransaction];
BOOL isRollBack = NO;
@try {
for (User *user in array) {
NSString *sql = [NSString stringWithFormat:@"INSERT INTO User(name, age, ID_No) VALUES ('%@', '%d', '%@');", user.name, user.age, user.ID_no];
BOOL res = [db executeUpdate:sql];
if (!res) {
NSLog(@"db事务插入失败");
}else {
NSLog(@"db事务插入成功");
}
}
}
@catch (NSException *exception) {
isRollBack =YES;
[db rollback];
}
@finally {
if (!isRollBack) {
[db commit];
}
}
[db close];
return !isRollBack;
}
更新与删除也分两种情形，与插入类似。
3、更新数据
/** 更新单个对象 */
- (BOOL)updateByDB
{
FMDatabase *db = [FMDatabase databaseWithPath:[User getDBPath]];
if (![db open]) {
NSLog(@"数据库打开失败!");
return NO;
}
NSString *sql = [NSString stringWithFormat:@"UPDATE User SET name = '%@',age = '%d',ID_no = '%@' WHERE ID = '%d';", self.name, self.age, self.ID_no, self.ID];
BOOL res = [db executeUpdate:sql];
[db close];
if (res) {
NSLog(@"插入数据成功");
}else {
NSLog(@"插入数据失败");
}
return res;
}
/** 批量更新用户对象*/
+ (BOOL)updateObjectsByDB:(NSArray *)array
{
FMDatabase *db = [FMDatabase databaseWithPath:[User getDBPath]];
if (![db open]) {
NSLog(@"数据库打开失败!");
return NO;
}
[db beginTransaction];
BOOL isRollBack = NO;
@try {
for (User *user in array) {
NSString *sql = [NSString stringWithFormat:@"UPDATE User SET name = '%@',age = '%d',ID_no = '%@' WHERE ID = '%d';", user.name, user.age, user.ID_no, user.ID];
BOOL res = [db executeUpdate:sql];
if (!res) {
NSLog(@"db事务更新失败");
}else {
NSLog(@"db事务更新成功");
}
}
}
@catch (NSException *exception) {
isRollBack =YES;
[db rollback];
}
@finally {
if (!isRollBack) {
[db commit];
}
}
[db close];
return !isRollBack;
}
4、删除数据
/** 删除单个对象 */
- (BOOL)deleteObjectByDB
{
FMDatabase *db = [FMDatabase databaseWithPath:[User getDBPath]];
if (![db open]) {
NSLog(@"数据库打开失败!");
return NO;
}
NSString *sql = [NSString stringWithFormat:@"DELETE FROM User WHERE ID = '%d'",self.ID];
BOOL res = [db executeUpdate:sql];
[db close];
if (res) {
NSLog(@"删除数据成功");
}else {
NSLog(@"删除数据失败");
}
return res;
}
/** 批量删除用户对象 */
+ (BOOL)deleteObjectsByDB:(NSArray *)array
{
FMDatabase *db = [FMDatabase databaseWithPath:[self getDBPath]];
if (![db open]) {
NSLog(@"数据库打开失败!");
return NO;
}
[db beginTransaction];
BOOL isRollBack = NO;
@try {
for (User *user in array) {
NSString *sql = [NSString stringWithFormat:@"DELETE FROM User WHERE ID = '%d'",user.ID];
BOOL res = [db executeUpdate:sql];
if (!res) {
NSLog(@"db事务删除失败");
}else {
NSLog(@"db事务删除成功");
}
}
}
@catch (NSException *exception) {
isRollBack =YES;
[db rollback];
}
@finally {
if (!isRollBack) {
[db commit];
}
}
[db close];
return !isRollBack;
}
5、查询数据
查询就比较简单了。
/** 查询全部用户 */
+ (NSArray *)findAllByDB
{
FMDatabase *db = [FMDatabase databaseWithPath:[self getDBPath]];
if (![db open]) {
NSLog(@"数据库打开失败!");
return nil;
}
NSMutableArray *users = [[NSMutableArray alloc] init];
NSString *sql = @"SELECT * FROM User";
FMResultSet *resultSet = [db executeQuery:sql];
while ([resultSet next]) {
User *user = [[User alloc] init];
user.ID = [resultSet intForColumn:@"ID"];
user.name = [resultSet stringForColumn:@"name"];
user.age = [resultSet intForColumn:@"age"];
user.ID_no = [resultSet stringForColumn:@"ID_no"];
[users addObject:user];
[user release];
}
NSLog(@"查询全部成功");
return [users autorelease];
}
/** 查找某个用户 */
+ (instancetype)findFirstBySqlByDB:(NSString *)sql
{
User *user = nil;
NSArray *users = [self findBySqlByDB:sql];
if (users.count > 0) {
user = [users firstObject];
}
return user;
}
/** 查找用户 */
+ (NSArray *)findBySqlByDB:(NSString *)sql
{
FMDatabase *db = [FMDatabase databaseWithPath:[self getDBPath]];
if (![db open]) {
NSLog(@"数据库打开失败!");
return nil;
}
NSMutableArray *users = [[NSMutableArray alloc] init];
NSString *select = @"SELECT * FROM User ";
if (sql) {
select = [select stringByAppendingString:sql];
}
FMResultSet *resultSet = [db executeQuery:select];
while ([resultSet next]) {
User *user = [[User alloc] init];
user.ID = [resultSet intForColumn:@"ID"];
user.name = [resultSet stringForColumn:@"name"];
user.age = [resultSet intForColumn:@"age"];
user.ID_no = [resultSet stringForColumn:@"ID_no"];
[users addObject:user];
[user release];
}
NSLog(@"条件查询成功");
return [users autorelease];
}
而多线程下的调用方式是这样的，其中上面的所有方法都是在对象类User中。
/** 用db插入User数据*/
- (IBAction)dbInsertData:(id)sender {
//多线程插入数据
for (int i = 0; i < 5; i++) {
dispatch_async(dispatch_get_global_queue(0, 0), ^{
User *user = [[User alloc] init];
user.name = @"dbName一";
user.ID_no = [NSString stringWithFormat:@"%d",55555+i];
user.age = 555+i;
[user saveByDB];
});
}
//利用事务插入数据
dispatch_async(dispatch_get_global_queue(0, 0), ^{
NSMutableArray *array = [NSMutableArray array];
for (int i = 0; i < 5; i++) {
User *user = [[User alloc] init];
user.name = @"db事务";
user.ID_no = [NSString stringWithFormat:@"%d",66666+i];
user.age = 66+i;
[array addObject:user];
[user release];
}
[User saveObjectsByDB:array];
});
}
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