Extent existing objectgraphs with typhoon

Let's say there are several kingdoms. Each kingdom has a castle. Now I want to create some knights for one of this kingdoms.

The interfaces look like this:

@interface Castle : NSObject
@end

@interface Kingdom : NSObject
@property(nonatomic, strong)Castle *castle;
@end

@interface Knight : NSObject
@property(nonatomic, strong)Castle *address;
@end

The actual internal implementation of the knights requires a reference to the castle. Here is my Definition:

-(Knight *)knight
{
    [TyphoonDefinition withClass:[Knight class] configuration:^(TyphoonDefinition *definition) {
        [definition injectProperty:@selector(address) with:[self castle]];
    }];
}

This is obvious wrong. What I want to express is "please create a knight for my kingdom and if you need a castle (or something else in my kingdom), then use the right one".

I could overcome this problem with a castle-runtime-argument. But the fact, that the knight needs this castle is an implementation detail. Maybe future knight implementations need something else.

I can achieve the behavior i want with the following code:

MiddleAgesAssembly* assembly = [[MiddleAgesAssembly assembly] activate];
id<TyphoonComponentsPool> objectGraphSharedInstances = [assembly valueForKeyPath:@"factory._objectGraphSharedInstances"];
    [objectGraphSharedInstances setObject:castle forKey:@selector(castle)];

[assembly knight];

This is not very elegant, but it solves the problem in this example.

A more general approach would be to register a custom TyphoonComponentsPool's in the factory with corresponding scopes for the definitions.

Are there any plans in this direction? Or maybe there is a better way to solve this kind of problems?

Thanks, Felix

Solution

Here's how to do it using Typhoon's current feature set:

Define a holder object with scope singleton, lazy singleton or weak singleton. This holder object has mutable properties or methods to pass in context objects.
Define other definitions that use the holder object as a factory.
Inject these into whatever you need.

As mentioned in comments, we're happy to explore alternative features/enhancements in the GitHub tracker.