FMDB的使用

#import "ViewController.h"
#import "FMDatabase.h"
#import "FMDatabaseQueue.h" //使用多线程时导入

@interface ViewController ()
@property (nonatomic, strong) FMDatabase *db;
@end

@implementation ViewController

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


#pragma - 建立表格
- (IBAction)create {
    
    //1.获得数据库文件的路径
    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
    doc = @"/Users/apple/Desktop/数据库";
    NSString *fileName = [doc stringByAppendingPathComponent:@"student.sqlite"];
    
    //2.获得数据库
    FMDatabase *db = [FMDatabase databaseWithPath:fileName];
    self.db = db;
    
    //3.使用如下语句，如果打开失败，可能是权限不足或者资源不足。通常打开完操作操作后，需要调用 close 方法来关闭数据库。在和数据库交互 之前，数据库必须是打开的。如果资源或权限不足无法打开或创建数据库，都会导致打开失败。
    if ([db open])
    {
        //4.建表
        BOOL result = [db executeUpdate:@"CREATE TABLE IF NOT EXISTS t_student (ID integer PRIMARY KEY AUTOINCREMENT, name text NOT NULL, age integer NOT NULL)"];
        if (result) {
            NSLog(@"建表成功!");
        }else {
            NSLog(@"建表失败!");
        }
    }
}

#pragma - 插入数据
- (IBAction)insert {
    
    NSString *name = @"张三";
    int age = 27;
    //方式1.executeUpdate:不确定的参数用 ？来占位（后面参数必须是oc对象，；代表语句结束）
    [self.db executeUpdate:@"INSERT INTO t_student (name, age) VALUES (?,?);",name,@(age)];
    
    //方式2.executeUpdateWithForamat：不确定的参数用%@，%d等来占位 （参数为原始数据类型，执行语句不区分大小写）
    [self.db executeUpdateWithFormat:@"insert into t_student (name,age) values (%@,%i);",name,age];
    
    //方式3.参数是数组的使用方式
    [self.db executeUpdate:@"INSERT INTO t_student(name,age) VALUES  (?,?);"withArgumentsInArray:@[name,@(age)]];

}

#pragma - 删除数据
- (IBAction)delete {
    
    //方式1.不确定的参数用 ？来占位（后面参数必须是oc对象,需要将int包装成OC对象）
    int idNum = 1;
    [self.db executeUpdate:@"delete from t_student where ID = ?;",@(idNum)];
    
    NSString *name = @"张三";
    //方式2.不确定的参数用%@，%d等来占位
    [self.db executeUpdateWithFormat:@"delete from t_student where name = %@;",name];
}

#pragma - 修改数据
- (IBAction)update {
    
    NSString *oldName = @"张三";
    NSString *newName = @"李四";
    //修改学生的名字
    [self.db executeUpdate:@"update t_student set name = ? where name = ?",newName,oldName];
}

#pragma - 查询数据
- (IBAction)select {
    /*
     FMResultSet获取不同数据格式的方法:
     
     intForColumn:
     longForColumn:
     longLongIntForColumn:
     boolForColumn:
     doubleForColumn:
     stringForColumn:
     dataForColumn:
     dataNoCopyForColumn:
     UTF8StringForColumnIndex:
     objectForColumn:
     */
    
    //查询整个表
    FMResultSet *resultSet1 = [self.db executeQuery:@"select * from t_student;"];
    
    //根据条件查询
    FMResultSet *resultSet2 = [self.db executeQuery:@"select * from t_student where id<?;",@(14)];
    
    //遍历结果集合
    while ([resultSet2  next])
        
    {
        int idNum = [resultSet2 intForColumn:@"ID"];
        
        NSString *name = [resultSet2 objectForColumnName:@"name"];
        
        int age = [resultSet2 intForColumn:@"age"];
    }
}

#pragma - 销毁命令
- (IBAction)drop {
    
    //如果表格存在 则销毁
    [self.db executeUpdate:@"drop table if exists t_student;"];
}

#pragma - 多线程的使用方法
- (void)method {
    
    NSString *aPath = @"......";
    //1.创建队列
    FMDatabaseQueue *queue = [FMDatabaseQueue
                              databaseQueueWithPath:aPath];
    __block BOOL whoopsSomethingWrongHappened = true;
    
    //2.把任务包装到事务里
    [queue inTransaction:^(FMDatabase *db, BOOL *rollback)
     {
         
         whoopsSomethingWrongHappened &= [db executeUpdate:@"INSERT INTO myTable VALUES (?)", [NSNumber numberWithInt:1]];
         whoopsSomethingWrongHappened &= [db executeUpdate:@"INSERT INTO myTable VALUES (?)", [NSNumber numberWithInt:2]];
         whoopsSomethingWrongHappened &= [db executeUpdate:@"INSERT INTO myTable VALUES (?)", [NSNumber numberWithInt:3]];
         //如果有错误 返回
         if (!whoopsSomethingWrongHappened)
         { 
             *rollback = YES;
             return;
         }
     }];
}

@end