Better you can use method to pass the data, like the following.
SDWebImageDataSource *imageController = [[SDWebImageDataSource alloc] init];
[imageController setImageLink:string1];
In you SDWebImageDataSource class, you can get the data from that method,
-(void)setImageLink:(NSString *)imageLinkStr
{
imageLink = imageLinkStr;
}
hope it will help you.