Question

So I’m building a system in which there is a server object, and it generates Uploader objects. Both are defined as protocols/interfaces, whichever term you prefer. The Server object has a method which generates an Uploader and returns it, with the following signature:

- (id<Uploader>)generateUploader;

The Uploader needs to contain a reference back to the Server which created it, because it needs a reference to a Server to get the password from my keychain wrapper. So, it contains a method which returns its parent Server:

- (id<VayprServer>)parentServer;

Of course, this creates a circular dependency between the two protocols. Any ideas on how to fix this?

Thanks!
Billy

Answer 1

To break the dependency, like all circular dependencies, you gotta forward-declare stuff in the .hs. In particular:

// VapyrServer.h

@protocol Uploader;

@interface Blah : …
…
- (id <Uploader>) generateUploader;
…

and

// VapyrServer.m

#import "Uploader.h"
…

and

// Uploader.h

@protocol VapyrServer;

@interface MoreBlah : …
…
- (id <VapyrServer>) parentServer;
…

and

// Uploader.m

#import "VapyrServer.h"
…

This way, the two .ms will see things declared in the correct order.