如何在 Core Data 中检查给定用户名的密码？ [关闭]

Posted 2023-03-04

【中文标题】如何在 Core Data 中检查给定用户名的密码？ [关闭]

【英文标题】：How to check the password for a given username in Core Data? [closed]

【发布时间】：2012-01-30 19:35:11

【问题描述】：

我有一个用户名 [字符串]，我想检查给定用户名的密码。我该怎么做？

【参考方案1】：

NSString *username = <#Username#>;
NSManagedObjectContext *context = <#Context#>;

NSFetchRequest *fetchRequest = [[[NSFetchRequest alloc] init] autorelease];
fetchRequest.entity = [NSEntityDescription entityForName:@"User" inManagedObjectContext:context]
fetchRequest.predicate = [NSPredicate predicateWithFormat:@"self.name == %@", username];
fetchRequest.fetchLimit = 1;

NSError *error = nil;
NSArray *users = [context executeFetchRequest:fetchRequest error:&error];

if (users.count > 0)

    NSString *password = [[users objectAtIndex:0] valueForKey:@"password"];

else if (error != nil)

    NSLog(@"User with given username does not exist.");

else

    NSLog(@"Error fetching user: %@", error);

【参考方案2】：

要在应用程序中查询给定用户名的密码的核心数据，您需要在执行查询时使用谓词。此示例假定您的实体名为 Users，您要查找的用户名名为 MyUser。

NSEntityDescription *entityDesc = [NSEntityDescription entityForName:@"Users"
                                              inManagedObjectContext:self.managedObjectContext];
NSFetchRequest *theRequest = [NSFetchRequest new];
[theRequest setEntity:entityDesc];
[theRequest setPredicate:[NSPredicate predicateWithFormat:@"username == %@",@"MyUser"]];
NSError *error;
NSArray *returnResults = [self.managedObjectContext executeFetchRequest:theRequest error:&error];
if (returnResults.count > 0) 
    NSManagedObject *MyUser = [returnResults objectAtIndex:0];
    NSString *password = [MyUser valueForKey:@"password"];
 else if (error != nil) 
    //Error
 else 
    //Error