NSArray排序

 NSArray *sortedArray = [messagessortedArrayUsingComparator:^NSComparisonResult(XMPPMessageArchiving_Message_CoreDataObject *p1,XMPPMessageArchiving_Message_CoreDataObject *p2){

        NSTimeInterval tempdate1= [[p1.messagegetPropertyValueByName:@"messagetime"]doubleValue];

        NSTimeInterval tempdate2= [[p2.messagegetPropertyValueByName:@"messagetime"]doubleValue];

        return tempdate1>tempdate2;

    }];