SQLite3第三方库之FMDB

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。在IOS中使用SQLite如果使用SDK提供的方法，特别麻烦也不利于理解和使用，在之前的blog.csdn.net/tangren03/a… API来使用数据库，感觉使用很不方便，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
//点击按钮后执行保存到数据库的操作  
- (IBAction)saveButtonClicked:(id)sender {  
    //获取Document文件夹下的数据库文件，没有则创建  
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];  
    NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"];  
      
    //获取数据库并打开  
    FMDatabase *database  = [FMDatabase databaseWithPath:dbPath];  
    if (![database open]) {  
        NSLog(@"Open database failed");  
        return;  
    }  
      
    //创建表（FMDB中只有update和query操作，出了查询其他都是update操作）  
    [database executeUpdate:@"create table user (name text,gender text,age integer)"];  
      
    //插入数据  
    BOOL insert = [database executeUpdate:@"insert into user values (?,?,?)",nameTextField.text,genderTextField.text,ageTextField.text];  
      
    if (insert) {  
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"保存成功" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];  
        [alert show];  
        [alert release];  
    }  
      
    [database close];  
}  

操作成功后弹出提示框：

[cpp]  view plain copy
//点击按钮后执行查询操作  
- (IBAction)queryButtonTapped:(id)sender {  
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  
    NSString *documentPath = [paths objectAtIndex:0];  
    NSString *dbPath = [documentPath stringByAppendingPathComponent:@"user.db"];  
      
    FMDatabase *database = [FMDatabase databaseWithPath:dbPath];  
    if (![database open]) {  
        return;  
    }  
      
    //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  
    FMResultSet *resultSet = [database executeQuery:@"select * from user"];  
    while ([resultSet next]) {  
        NSString *name = [resultSet stringForColumn:@"name"];  
        NSString *gender = [resultSet stringForColumn:@"gender"];  
        int age = [resultSet intForColumn:@"age"];  
        NSLog(@"Name:%@,Gender:%@,Age:%d",name,gender,age);  
          
    }  
      
    [database close];  
    //这里也不需要release  
//    [database release];  
}  

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
//执行条件查询操作  
- (IBAction)queryByConditionBtnTapped:(id)sender {  
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  
    NSString *docPath = [paths objectAtIndex:0];  
    NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"];  
      
    FMDatabase *database = [FMDatabase databaseWithPath:dbPath];  
    if (![database open]) {  
        return;  
    }  
      
    FMResultSet *resultSet = [database executeQuery:@"select * from user where name = ?",@"Ryan"];  
    while ([resultSet next]) {  
        NSString *name = [resultSet stringForColumn:@"name"];  
        NSString *gender = [resultSet stringForColumn:@"gender"];  
        int age = [resultSet intForColumn:@"age"];  
        NSLog(@"Name:%@,Gender:%@,Age:%d",name,gender,age);  
    }  
      
    [database close];  
}  

[cpp]  view plain copy
//执行更新操作  
- (IBAction)updateBtnTapped:(id)sender {  
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  
    NSString *docPath = [paths objectAtIndex:0];  
    NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"];  
      
    FMDatabase *database = [FMDatabase databaseWithPath:dbPath];  
    if (![database open]) {  
        return;  
    }  
      
    //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  
    BOOL update = [database executeUpdate:@"update user set name = ? where age = ?",@"RyanTang",[NSNumber numberWithInt:24]];  
  
    if(update){  
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"更新成功" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];  
        [alert show];  
        [alert release];  
    }  
  
    [database close];  
}  

[cpp]  view plain copy
//执行删除操作  
- (IBAction)deleteBtnTapped:(id)sender {  
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  
    NSString *docPath = [paths objectAtIndex:0];  
    NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"];  
      
    FMDatabase *database = [FMDatabase databaseWithPath:dbPath];  
    if (![database open]) {  
        return;  
    }  
  
    BOOL delete = [database executeUpdate:@"delete from user where name = ?",@"Tang"];  
    if (delete) {  
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:@"删除成功" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];  
        [alert show];  
        [alert release];  
  
    }  
      
    [database close];  
}  

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
-(void)executeDBOperation  
{  
    //获取Document文件夹下的数据库文件，没有则创建  
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];  
    NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"];  
      
    FMDatabaseQueue *databaseQueue = [FMDatabaseQueue databaseQueueWithPath:dbPath];  
    [databaseQueue inDatabase:^(FMDatabase *db){  
    [db executeUpdate:@"insert into user values (?,?,?)",@"Ren",@"Male",[NSNumber numberWithInt:20]];  
    }];  
    [databaseQueue close];  
}  

工程源码：下载

（原文：blog.csdn.net/ryantang03/…