Function kosCompanion

Class decorator that adds companion model capabilities to a KOS model.

Supports two patterns:

1. Decorator Pattern (default): Transparently proxies all parent properties, making the companion a drop-in replacement for the parent
2. Composition Pattern: Only provides getCompanionParent() method, keeping parent encapsulated

Important: Use TypeScript interface merging to get proper type information:

// Decorator pattern - full transparency
interface BrandCompanionModelImpl extends KosCompanionAware<AvailabilityModel> {}

@kosModel("brand-companion")
@kosCompanion() // defaults to decorator mode
class BrandCompanionModelImpl implements IKosDataModel {
  // All parent properties are available
  get brandSpecificProperty() {
    return this.name; // 'name' from parent AvailabilityModel
  }
}

// Composition pattern - encapsulated parent
interface ServiceCompanionModelImpl extends KosCompanionAware<ServiceModel> {}

@kosModel("service-companion")
@kosCompanion({ mode: 'composition' })
class ServiceCompanionModelImpl implements IKosDataModel {
  // Parent is only accessible via getCompanionParent()
  get serviceInfo() {
    const parent = this.getCompanionParent();
    return `Service: ${parent.serviceName}`;
  }
}
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Example

// Decorator mode - all parent properties proxied
@kosCompanion()
class MyCompanion { }

// Composition mode - only getCompanionParent() available
@kosCompanion({ mode: 'composition' })
class MyCompanion { }

// Decorator mode with exclusions
@kosCompanion({ mode: 'decorator', excludeProperties: ['internalState'] })
class MyCompanion { }

// Lifecycle-deferred companion creation
@kosCompanion({ lifecycle: DependencyLifecycle.LOAD })
class DataDrivenCompanion { }
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Since

2.1.0