NSUrlCache removeCachedResponseForRequest:requestImage implementation in objective c

Question

I want to store the response fetched from a request in NSUrlCache.How. How can this be done?

-(void)sendRequestForImage

{  

    NSCachedURLResponse * cachedResponse = [Cache cachedResponseForRequest:requestImage];

    if(!cachedResponse.data)

    {
     NSString*imageStr=[NetworkManger getImage:requestImage]; 
        _imageView.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imageStr]]];

    }

    else

    { 
        NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:cachedResponse.data options:NSJSONReadingAllowFragments error:nil];    


      }   
}

Now I am trying to remove the object for request requestImage and I am trying to do this as follows:

- (IBAction)clearImage:(id)sender {

    [Cache removeCachedResponseForRequest:requestImage];
   }

But this doesn't work. Why?