IOS-FMDB

一、FMDB简介

什么是FMDB

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

 

FMDB的优点

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

对比苹果自带的Core Data框架，更加轻量级和灵活

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的github地址

https://github.com/ccgus/fmdb

 

二、核心类

FMDB有三个主要的类

FMDatabase

一个FMDatabase对象就代表一个单独的SQLite数据库

用来执行SQL语句

 

FMResultSet

使用FMDatabase执行查询后的结果集

 

FMDatabaseQueue

用于在多线程中执行多个查询或更新，它是线程安全的

 

三、打开数据库

通过指定SQLite数据库文件路径来创建FMDatabase对象

FMDatabase *db = [FMDatabase databaseWithPath:path];

if (![db open]) {

    NSLog(@"数据库打开失败！");

}

 

文件路径有三种情况

具体文件路径

如果不存在会自动创建

 

空字符串@""

会在临时目录创建一个空的数据库

当FMDatabase连接关闭时，数据库文件也被删除

 

nil

会创建一个内存中临时数据库，当FMDatabase连接关闭时，数据库会被销毁

 

 

四、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

- (BOOL)executeUpdate:(NSString*)sql, ...

- (BOOL)executeUpdateWithFormat:(NSString*)format, ...

- (BOOL)executeUpdate:(NSString*)sql withArgumentsInArray:(NSArray *)arguments

 

示例

[db executeUpdate:@"UPDATE t_student SET age = ? WHERE name = ?;", @20, @"Jack"]

五、执行查询

查询方法

- (FMResultSet *)executeQuery:(NSString*)sql, ...

- (FMResultSet *)executeQueryWithFormat:(NSString*)format, ...

- (FMResultSet *)executeQuery:(NSString *)sql withArgumentsInArray:(NSArray *)arguments

 

示例

// 查询数据

FMResultSet *rs = [db executeQuery:@"SELECT * FROM t_student"];

// 遍历结果集

while ([rs next]) {

    NSString *name = [rs stringForColumn:@"name"];

    int age = [rs intForColumn:@"age"];

    double score = [rs doubleForColumn:@"score"];

}

六、FMDatabaseQueue

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

 

FMDatabaseQueue的创建

FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath:path];

简单使用

[queue inDatabase:^(FMDatabase *db) {

    [db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jack"];

    [db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Rose"];

    [db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jim"];

   

    FMResultSet *rs = [db executeQuery:@"select * from t_student"];

    while ([rs next]) {

        // …

    }

}];

使用事务

[queue inTransaction:^(FMDatabase *db, BOOL *rollback) {

    [db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jack"];

    [db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Rose"];

    [db executeUpdate:@"INSERT INTO t_student(name) VALUES (?)", @"Jim"];

   

    FMResultSet *rs = [db executeQuery:@"select * from t_student"];

    while ([rs next]) {

        // …

    }

}];

事务回滚

*rollback = YES;

我的代码

//
//  ViewController.m
//  IOS_0331_SQLite3
//
//  Created by ma c on 16/3/31.
//  Copyright © 2016年 博文科技. All rights reserved.
//

#import "ViewController.h"
#import "FMDB.h"

@interface ViewController ()

@property (nonatomic, strong) FMDatabase *db;


- (IBAction)insert;
- (IBAction)update;
- (IBAction)query;
- (IBAction)delete;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self createDatabase];
}

- (void)createDatabase
{
    // 0.获得沙盒中的数据库文件名
    NSString *fileName = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"student.sqlite"];
    NSLog(@"%@",fileName);
    
    // 1.创建数据库实例对象
    self.db = [FMDatabase databaseWithPath:fileName];
    
    // 2.打开数据库
    if ([self.db open]) {
        NSLog(@"数据库打开成功");
        
        //创表
        BOOL flag = [self.db executeUpdate:@"create table if not exists t_student (id integer primary key autoincrement, name text, age integer) ;"];
        if (flag) {
            NSLog(@"建表成功");
        } else {
            NSLog(@"建表失败");
        }
    } else {
        NSLog(@"数据库打开失败");
    }
}

- (IBAction)insert {
    
    [self.db executeUpdate:@"insert into t_student (name, age) values (?, ?);",@"rose",@10];

}

- (IBAction)update {
    
    [self.db executeUpdate:@"update t_student set age = ? where name = ?;",@20, @"rose"];
}

- (IBAction)query {
    //1.查询数据
    FMResultSet *rs = [self.db executeQuery:@"select * from t_student;"];
    //2.遍历结果集
    while (rs.next) {
        int ID = [rs intForColumn:@"id"];
        NSString *name = [rs stringForColumn:@"name"];
        int age = [rs intForColumn:@"age"];
        
        NSLog(@"%d %@ %d",ID, name, age);
    }
    
}

- (IBAction)delete {
    
    [self.db executeUpdate:@"delete from t_student where name = ?;",@"rose"];

}
@end

线程安全和事物

//
//  IWViewController.m
//  01-SQLite的基本使用
//
//  Created by apple on 14-5-22.
//  Copyright (c) 2014年 itcast. All rights reserved.
//

#import "IWViewController.h"
#import "FMDB.h"

@interface IWViewController ()
@property (nonatomic, strong) FMDatabaseQueue *queue;
- (IBAction)insert;
- (IBAction)update;
- (IBAction)delete;
- (IBAction)query;
@end

@implementation IWViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // 0.获得沙盒中的数据库文件名
    NSString *filename = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"student.sqlite"];
    
    // 1.创建数据库队列
    self.queue = [FMDatabaseQueue databaseQueueWithPath:filename];
    
    // 2.创表
    [self.queue inDatabase:^(FMDatabase *db) {
        BOOL result = [db executeUpdate:@"create table if not exists t_student (id integer primary key autoincrement, name text, age integer);"];
        
        if (result) {
            NSLog(@"创表成功");
        } else {
            NSLog(@"创表失败");
        }
    }];
}

- (IBAction)insert
{
    [self.queue inDatabase:^(FMDatabase *db) {
        for (int i = 0; i<40; i++) {
            NSString *name = [NSString stringWithFormat:@"rose-%d", arc4random() % 1000];
            NSNumber *age = @(arc4random() % 100 + 1);
            [db executeUpdate:@"insert into t_student (name, age) values (?, ?);", name, age];
        }
    }];
}

- (IBAction)update
{
    [self.queue inDatabase:^(FMDatabase *db) {
        // 开启事务
//        [db executeUpdate:@"begin transaction;"];
//        [db beginTransaction];
        
        [db executeUpdate:@"update t_student set age = ? where name = ?;", @20, @"jack"];
        [db executeUpdate:@"update t_student set age = ? where name = ?;", @20, @"jack"];
        
        
//        if (发现情况不对){
//            // 回滚事务
//            [db rollback];
////            [db executeUpdate:@"rollback transaction;"];
//        }
        
        
        [db executeUpdate:@"update t_student set age = ? where name = ?;", @20, @"jack"];
        
        // 提交事务
//        [db commit];
//        [db executeUpdate:@"commit transaction;"];
    }];
}

- (IBAction)delete
{
    [self.queue inTransaction:^(FMDatabase *db, BOOL *rollback) {
        [db executeUpdate:@"update t_student set age = ? where name = ?;", @20, @"jack"];
        [db executeUpdate:@"update t_student set age = ? where name = ?;", @20, @"jack"];
        
//        if (发现情况不对){
//            // 回滚事务
//            *rollback = YES;
//        }
    }];
}

- (IBAction)query
{
    [self.queue inDatabase:^(FMDatabase *db) {
        // 1.查询数据
        FMResultSet *rs = [db executeQuery:@"select * from t_student where age > ?;", @50];
        
        // 2.遍历结果集
        while (rs.next) {
            int ID = [rs intForColumn:@"id"];
            NSString *name = [rs stringForColumn:@"name"];
            int age = [rs intForColumn:@"age"];
            
            NSLog(@"%d %@ %d", ID, name, age);
        }
    }];
}
@end