NSError *error;
NSManagedObjectContext *context = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
NSEntityDescription *entityDesc = [NSEntityDescription entityForName:@"Tz_task_from" inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc]init];
[request setEntity:entityDesc];
[request setReturnsObjectsAsFaults:NO];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"taskfrom=%@",userid];
[request setPredicate:predicate];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"taskend" ascending:NO];
NSArray*sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor,nil];
[request setSortDescriptors:sortDescriptors];
NSArray *objects = [context executeFetchRequest:request error:&error];
1、比较运算符>,<,==,>=,<=,!=
2、范围运算符：IN、BETWEEN
3、字符串本身:SELF
4、字符串相关：
（1）、CONTAINS包含某个字符串
@nameCONTAINS[cd] %@
（2）、BEGINSWITH以某个字符串开头
@nameBEGINSWITH[c] %@
（3）、ENDSWITH以某个字符串结束
@nameENDSWITH[d] %@
注:
[c]不区分大小写
[d]不区分发音符号即没有重音符号
[cd]既不区分大小写，也不区分发音符号。
5、通配符：LIKE
例：[NSPredicate predicateWithFormat:[NSString stringWithFormat:@"customername LIKE[cd] '*%@*'",_searchString]];
6、正则表达式：MATCHES
例：NSString *regex = @"^A.+e$"; //以A开头，e结尾
@"name MATCHES %@",regex
