ios - although I add the header file, class is not seen on Objective-C -

i have added header file view controller , creating instance of class, taking undefined symbols

architecture i386: "_objc_class_$_medicinedownloadsview", referenced from: error.

how fix it?

my main view controller follows;

header file

#import <uikit/uikit.h> #import "medicinedownloadsview.h"  @interface viewcontroller : uiviewcontroller {    medicinedownloadsview *medicinedownload; }  @property (nonatomic,retain) medicinedownloadsview *medicinedownload; @end 

main file

#import "viewcontroller.h"  @interface viewcontroller ()  @end  @implementation viewcontroller @synthesize medicinedownload;  - (void)viewdidload {    [super viewdidload];     medicinedownload = [[medicinedownloadsview alloc]init];     self.view = medicinedownload; }  @end 

check medicinedownloadsview.m added "compile sources" build phase of target.