Question

Recently I downloaded the open source project zbar, the project itself it not really relevant to my question, what I still can’t figure out is how in his viewcontroller he is able to do this:

//
//  EmbedReaderViewController.h
//  EmbedReader
//
//  Created by spadix on 5/2/11.
//

#import <UIKit/UIKit.h>

@interface EmbedReaderViewController
    : UIViewController
    < ZBarReaderViewDelegate >
{
    ZBarReaderView *readerView;
    UITextView *resultText;
    ZBarCameraSimulator *cameraSim;
}

@property (nonatomic, retain) IBOutlet ZBarReaderView *readerView;
@property (nonatomic, retain) IBOutlet UITextView *resultText;

@end

That is it, that is the whole file, how can he see the delegate and the ZBarReaderView and ZBarCameraSimulator, without importing anything???.

My implementation is working, but I of course have to import the files, and as I was looking at the example, it really caught my attention that he was not importing anything… how is that possible??

Answer 1

Projects usually have a pch file (pre-compiled/prefix header) in them; this file is automatically included in every other code file of the project. If the pch file contains an #import to the protocol file, then every file in the project will be aware of it.