摘要:本文将带了解IOS开发之SQLite3是什么,希望本文对大家学IOS有所帮助。
SQLite是一种小型的轻量级的关系型数据库,在移动设备上使用是非常好的选择,无论是Android还是IOS,都内置了SQLite数据库,现在的版本都是SQLite3。
今天就讲讲一个针对IOS的SQlite API封装的第三方库FMDB,FMDB对SDK中的API做了一层封装,使之使用OC来访问,使用方便而且更熟悉。FMDB的下载地址https://github.com/ccgus/fmdb。
FMDB主要涉及两个类,FMDatabase和FMResultSet,前者类似于Android中的SQLiteOpenHelper或SQLiteDatabase,FMResultSet类似于Android中的Cursor,用来存储结果集。
下载完FMDB源码后把文件拖到工程中,并导入SQLite支持库,工程目录如下:
然后就是这个Demo的完整截图:
然后就来看看如何操作FMDB:
[cpp] view plain copy 1. //点击按钮后执行保存到数据库的操作 2. - (IBAction)saveButtonClicked:(id)sender { 3. //获取Document文件夹下的数据库文件,没有则创建 4. NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; 5. NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"]; 6. 7. //获取数据库并打开 8. FMDatabase *database = [FMDatabase databaseWithPath:dbPath]; 9. if (![database open]) { 10. NSLog(@"Open database failed"); 11. return; 12. } 13. 14. //创建表(FMDB中只有update和query操作,出了查询其他都是update操作) 15. [database executeUpdate:@"create table user (name text,gender text,age integer)"]; 16. 17. //插入数据 18. BOOL insert = [database executeUpdate:@"insert into user values (?,?,?)",nameTextField.text,genderTextField.text,ageTextField.text]; 19. 20. if (insert) { 21. UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"保存成功" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil, nil]; 22. [alert show]; 23. [alert release]; 24. } 25. 26. [database close]; 27. }
操作成功后弹出提示框:
[cpp] view plain copy 1. //点击按钮后执行查询操作 2. - (IBAction)queryButtonTapped:(id)sender { 3. NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 4. NSString *documentPath = [paths objectAtIndex:0]; 5. NSString *dbPath = [documentPath stringByAppendingPathComponent:@"user.db"]; 6. 7. FMDatabase *database = [FMDatabase databaseWithPath:dbPath]; 8. if (![database open]) { 9. return; 10. } 11. 12. //不需要像Android中那样关闭Cursor关闭FMResultSet,因为相关的数据库关闭时,FMResultSet也会被自动关闭 13. FMResultSet *resultSet = [database executeQuery:@"select * from user"]; 14. while ([resultSet next]) { 15. NSString *name = [resultSet stringForColumn:@"name"]; 16. NSString *gender = [resultSet stringForColumn:@"gender"]; 17. int age = [resultSet intForColumn:@"age"]; 18. NSLog(@"Name:%@,Gender:%@,Age:%d",name,gender,age); 19. 20. } 21. 22. [database close]; 23. //这里也不需要release 24. // [database release]; 25. }
FMResultSet还支持以下方式获取值: · intForColumn: · longForColumn: · longLongIntForColumn: · boolForColumn: · doubleForColumn: · stringForColumn: · dateForColumn: · dataForColumn: · dataNoCopyForColumn: · UTF8StringForColumnIndex: · objectForColumn: [cpp] view plain copy 1. //执行条件查询操作 2. - (IBAction)queryByConditionBtnTapped:(id)sender { 3. NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 4. NSString *docPath = [paths objectAtIndex:0]; 5. NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"]; 6. 7. FMDatabase *database = [FMDatabase databaseWithPath:dbPath]; 8. if (![database open]) { 9. return; 10. } 11. 12. FMResultSet *resultSet = [database executeQuery:@"select * from user where name = ?",@"Ryan"]; 13. while ([resultSet next]) { 14. NSString *name = [resultSet stringForColumn:@"name"]; 15. NSString *gender = [resultSet stringForColumn:@"gender"]; 16. int age = [resultSet intForColumn:@"age"]; 17. NSLog(@"Name:%@,Gender:%@,Age:%d",name,gender,age); 18. } 19. 20. [database close]; 21. } [cpp] view plain copy 1. //执行更新操作 2. - (IBAction)updateBtnTapped:(id)sender { 3. NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 4. NSString *docPath = [paths objectAtIndex:0]; 5. NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"]; 6. 7. FMDatabase *database = [FMDatabase databaseWithPath:dbPath]; 8. if (![database open]) { 9. return; 10. } 11. 12. //参数必须是NSObject的子类,int,double,bool这种基本类型,需要封装成对应的包装类才可以 13. BOOL update = [database executeUpdate:@"update user set name = ? where age = ?",@"RyanTang",[NSNumber numberWithInt:24]]; 14. 15. if(update){ 16. UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"更新成功" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil, nil]; 17. [alert show]; 18. [alert release]; 19. } 20. 21. [database close]; 22. }
[cpp] view plain copy 1. //执行删除操作 2. - (IBAction)deleteBtnTapped:(id)sender { 3. NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 4. NSString *docPath = [paths objectAtIndex:0]; 5. NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"]; 6. 7. FMDatabase *database = [FMDatabase databaseWithPath:dbPath]; 8. if (![database open]) { 9. return; 10. } 11. 12. BOOL delete = [database executeUpdate:@"delete from user where name = ?",@"Tang"]; 13. if (delete) { 14. UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"删除成功" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil, nil]; 15. [alert show]; 16. [alert release]; 17. 18. } 19. 20. [database close]; 21. }
如果我们的app需要多线程操作数据库,那么就需要使用FMDatabaseQueue来保证线程安全了。切记不能在多个线程中共同一个FMDatabase对象并且在多个线程中同时使用,这个类本身不是线程安全的,这样使用会造成数据混乱等问题。
使用FMDatabaseQueue很简单,首先用一个数据库文件地址来初使化FMDatabaseQueue,然后就可以将一个闭包(block)传入inDatabase方法中。在闭包中操作数据库,而不直接参与FMDatabase的管理。
[cpp] view plain copy 1. -(void)executeDBOperation 2. { 3. //获取Document文件夹下的数据库文件,没有则创建 4. NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; 5. NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"]; 6. 7. FMDatabaseQueue *databaseQueue = [FMDatabaseQueue databaseQueueWithPath:dbPath]; 8. [databaseQueue inDatabase:^(FMDatabase *db){ 9. [db executeUpdate:@"insert into user values (?,?,?)",@"Ren",@"Male",[NSNumber numberWithInt:20]]; 10. }]; 11. [databaseQueue close]; 12. }
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