SQLite是一種小型的輕量級的關系型數據庫，在移動設備上使用是非常好的選擇，無論是Android還是IOS，都內置了SQLite數據庫，現在的版本都是SQLite3。在IOS中使用SQLite如果使用SDK提供的方法，特別麻煩也不利于理解和使用，在之前的http://blog.csdn.net/tangren03/article/details/7781930文章中就是使用IOS的SDK自帶的SQLite API來使用數據庫，感覺使用很不方便，今天就講講一個針對IOS的SQlite API封裝的第三方庫FMDB，FMDB對SDK中的API做了一層封裝，使之使用OC來訪問，使用方便而且更熟悉。FMDB的下載地址https://github.com/ccgus/fmdb。

FMDB主要涉及兩個類，FMDatabase和FMResultSet，前者類似于Android中的SQLiteOpenHelper或SQLiteDatabase，FMResultSet類似于Android中的Cursor，用來存儲結果集。

下載完FMDB源碼后把文件拖到工程中，并導入SQLite支持庫，工程目錄如下：

然后就是這個Demo的完整截圖：

然后就來看看如何操作FMDB:

//點擊按鈕后執行保存到數據庫的操作
- (IBAction)saveButtonClicked:(id)sender {
    //獲取Document文件夾下的數據庫文件，沒有則創建
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *dbPath = [docPath stringByAppendingPathComponent:@"user.db"];
    
    //獲取數據庫并打開
    FMDatabase *database  = [FMDatabase databaseWithPath:dbPath];
    if (![database open]) {
        NSLog(@"Open database failed");
        return;
    }
    
    //創建表（FMDB中只有update和query操作，出了查詢其他都是update操作）
    [database executeUpdate:@"create table user (name text,gender text,age integer)"];
    
    //插入數據
    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:@"確定" otherButtonTitles:nil, nil];
        [alert show];
        [alert release];
    }
    
    [database close];
}

操作成功后彈出提示框：

//點擊按鈕后執行查詢操作
- (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中那樣關閉Cursor關閉FMResultSet，因為相關的數據庫關閉時，FMResultSet也會被自動關閉
    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];
    //這里也不需要release
//    [database release];
}

FMResultSet還支持以下方式獲取值：

• intForColumn:
• longForColumn:
• longLongIntForColumn:
• boolForColumn:
• doubleForColumn:
• stringForColumn:
• dateForColumn:
• dataForColumn:
• dataNoCopyForColumn:
• UTF8StringForColumnIndex:
• objectForColumn:

//執行條件查詢操作
- (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];
}

//執行更新操作
- (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;
    }
    
    //參數必須是NSObject的子類，int,double,bool這種基本類型，需要封裝成對應的包裝類才可以
    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:@"確定" otherButtonTitles:nil, nil];
        [alert show];
        [alert release];
    }

    [database close];
}

//執行刪除操作
- (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:@"刪除成功" delegate:self cancelButtonTitle:@"確定" otherButtonTitles:nil, nil];
        [alert show];
        [alert release];

    }
    
    [database close];
}

如果我們的app需要多線程操作數據庫，那么就需要使用FMDatabaseQueue來保證線程安全了。切記不能在多個線程中共同一個FMDatabase對象并且在多個線程中同時使用，這個類本身不是線程安全的，這樣使用會造成數據混亂等問題。

使用FMDatabaseQueue很簡單，首先用一個數據庫文件地址來初使化FMDatabaseQueue，然后就可以將一個閉包(block)傳入inDatabase方法中。在閉包中操作數據庫，而不直接參與FMDatabase的管理。

-(void)executeDBOperation
{
    //獲取Document文件夾下的數據庫文件，沒有則創建
    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];
}

歡迎關注我的新浪微博和我交流：@唐韌_Ryan