FMDB的线程安全和事务

最新推荐文章于 2019-01-28 15:56:50 发布

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最新推荐文章于 2019-01-28 15:56:50 发布

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分类专栏： iOS

本文链接：https://blog.youkuaiyun.com/github_26672553/article/details/48810603

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本文介绍了一个使用FMDB进行线程安全操作及事务处理的iOS应用案例。通过FMDatabaseQueue实现数据库操作的线程安全，并演示了如何执行插入、查询、更新和删除操作。同时展示了如何在FMDB中正确地使用事务来确保数据的一致性和完整性。

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//
//  ViewController.m
//  FMDB的线程安全和事务
//


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

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

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    //0.获得沙盒中的数据库文件名
    //沙盒caches目录：NSCachesDirectory
    //沙盒Document目录：NSDocumentDirectory
    NSString *filename = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"student.sqlite"];
    
    //1.创建数据库实例队列
    self.queue = [FMDatabaseQueue databaseQueueWithPath:filename];
    
    //2.建表
    [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(@"建表成功");
        }else{
            NSLog(@"建表失败");
        }
    }];
    

    
}



- (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)query {
    [self.queue inDatabase:^(FMDatabase *db) {
        //1.查询数据
        FMResultSet *rs = [db executeQuery:@"select * from t_student where age>?;",@80];
        
        //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)update {
    [self.queue inDatabase:^(FMDatabase *db) {
        //开启事务
//        [db beginTransaction];
        
        [db executeUpdate:@"update t_student set age=? where name=?;",@20,@"jack"];
        [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:@"update t_student set age=? where name=?;",@20,@"jack"];
        
        //提交事务
//        [db commit];
    }];
}

- (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;
//        }
    }];
}


@end