Ios 我们如何更新使用核心数据存储的属性值？

我在应用程序中使用了核心数据来保存用户数据。单个用户有“用户名”、“密码”、“确认密码”、“手机号码”

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我可以保存注册用户信息，也可以验证用户名和密码，并登录到应用程序。现在我想改变我的“密码”，如果用户输入“用户名”，“手机号码”正确。如何执行此操作？

这与保存注册用户信息相同

// Set password and save
[user setPassword:newPassword];
[user.managedObjectContext save:nil];

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从核心数据检索对象后，使用谓词更新对象，然后保存它

例：

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将用户信息更新到数据库中

 NSEntityDescription *productEntity=[NSEntityDescription entityForName:@"Registration" inManagedObjectContext:context];


        NSFetchRequest *fetch=[[NSFetchRequest alloc] init];
        [fetch setEntity:productEntity];
        NSPredicate *p=[NSPredicate predicateWithFormat:@"username == %@ AND mail_no == %@",user-username,mobile_no];
        [fetch setPredicate:p];
        //... add sorts if you want them
        NSError *fetchError;
        NSArray *fetchedProducts=[context executeFetchRequest:fetch error:&fetchError];

        NSLog(@" update fetch data %@", fetchedProducts);

        for (NSManagedObject *record in fetchedProducts) {

            [record setValue:_mailTextField.text forKey:@"mailID"];

        }

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这是我用来更改密码的代码。我使用“用户名”和“旧密码”更改密码。很好用

NSEntityDescription *entitydesc = [NSEntityDescription entityForName:@"User" inManagedObjectContext:context];

NSFetchRequest *request = [[NSFetchRequest alloc]init];
[request setEntity:entitydesc];

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"username like %@ and password like %@",username,self.oldPass.text];
[request setPredicate:predicate];

NSError *error;
NSArray *matchingData = [context executeFetchRequest:request error:&error];

if(matchingData.count<=0)
  {
      UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Error!" message:@"Old Password Does not Match" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
      [alert show];
  }
else
  {
      for(NSManagedObject *obj in matchingData)
      {
          [obj setValue:changedPass.text forKey:@"password"];
          [obj setValue:confirmChangedPass.text forKey:@"confirmpassword"];
      }
          [context save:&error];
          alert1 = [[UIAlertView alloc]initWithTitle:@"Success" message:@"Password Changed Successfully" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
          [alert1 show];
   }
}

NSEntityDescription*entitydesc=[NSEntityDescription entityForName:@“User”inManagedObjectContext:context]；
NSFetchRequest*request=[[NSFetchRequest alloc]init]；
[请求集合实体：entitydesc]；
NSPredicate*谓词=[NSPredicate谓词格式：@“类似用户名%@和密码%@”，用户名，self.oldPass.text]；
[请求集谓词：谓词]；
n错误*错误；
NSArray*matchingData=[context executeFetchRequest:请求错误：&error]；
如果（matchingData.count）我知道完整的解决方案，请告诉我您使用了哪个字段作为主键为什么取消选中我的答案。为什么删除接受的答案对不起，谢谢您的答案。另外，我将我的代码放在我所做的事情上。感谢您的贡献。这个声誉是为了我的效果
NSEntityDescription *entitydesc = [NSEntityDescription entityForName:@"User" inManagedObjectContext:context];

NSFetchRequest *request = [[NSFetchRequest alloc]init];
[request setEntity:entitydesc];

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"username like %@ and password like %@",username,self.oldPass.text];
[request setPredicate:predicate];

NSError *error;
NSArray *matchingData = [context executeFetchRequest:request error:&error];

if(matchingData.count<=0)
  {
      UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Error!" message:@"Old Password Does not Match" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
      [alert show];
  }
else
  {
      for(NSManagedObject *obj in matchingData)
      {
          [obj setValue:changedPass.text forKey:@"password"];
          [obj setValue:confirmChangedPass.text forKey:@"confirmpassword"];
      }
          [context save:&error];
          alert1 = [[UIAlertView alloc]initWithTitle:@"Success" message:@"Password Changed Successfully" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
          [alert1 show];
   }
}