ios - 用于电子邮件问题的 NSPredicate predicateWithFormat

Question

我在使用 predicateWithFormat 方法创建 NSPredicate 类型对象时遇到问题。

AppDelegate *appdelegateObj = (AppDelegate *)[[UIApplication sharedApplication] delegate];

self.managedObjectContext = [appdelegateObj managedObjectContext];
NSString *emailWithBackslashedAtTheRate = [email stringByReplacingOccurrencesOfString:@"@" withString:@"\\@"];

NSFetchRequest *fetchRequestObj = [NSFetchRequest fetchRequestWithEntityName:@"Usertable"];
NSMutableArray *dataList;

**NSPredicate *predicate = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"email CONTAINS[c] %@",emailWithBackslashedAtTheRate]];**
[fetchRequestObj setPredicate:predicate];

@synchronized(delegate.persistentStoreCoordinator) {

    NSError *error = nil;
    NSMutableArray *filteredUser = (NSMutableArray *)[self.managedObjectContext executeFetchRequest:fetchRequestObj error:&error];
}

谁能解释一下，问题是什么？

Answer 1

在您的用户表中，字段名称 Email 必须是字符串。

 AppDelegate *coreAppDelegate=[[UIApplication sharedApplication]delegate];
        NSManagedObjectContext *context=[coreAppDelegate managedObjectContext];
        NSEntityDescription *entityDecs=[NSEntityDescription entityForName:@"UserDetail" inManagedObjectContext:context];
        NSFetchRequest *request =[[NSFetchRequest alloc]init];
        [request setEntity:entityDecs];
        //  NSLog(@"username = %@",mutarr);
        NSPredicate *pred=[NSPredicate predicateWithFormat:@"(email=%@)",TxtEmail];
        [request setPredicate:pred];
        NSManagedObject *matches =nil;
        NSError *error;