ISubscriber

ISubscriber defines the minimal interface for any component that consumes events via EventBus. It provides a stable identity and declares the delivery mode (push or pull).

struct ISubscriber {
  virtual SubscriberId id() const = 0;
  virtual SubscriberMode mode() const { return SubscriberMode::PUSH; }
};

using SubscriberId = uint64_t;
enum class SubscriberMode {
  PUSH,
  PULL
};

Purpose

• Abstract base for all event consumers, enabling uniform routing and delivery control.

Responsibilities

Method	Description
id()	Returns a globally unique ID for this subscriber.
mode()	Declares delivery mode: PUSH (default) or PULL (manual drain).

Notes

• PUSH mode: the bus invokes the subscriber immediately on event dispatch.
• PULL mode: the subscriber drains from a queue explicitly (e.g., with batching).
• SubscriberId is typically derived from pointer identity or hash — no strong ownership implied.
• Used by EventBus<T> to track subscribers and apply fan-out policy.