OnSignal

Type

Method decorator.

About

Marks method as signal handler. Every signal event with provided type will be handled by a service instance.
Services handlers priority is same as instantiation order.

Mainly used to register signal events handlers with generic logic that reacts on application events.

Call Signature

type SignalType = symbol | string | number;

@OnSignal(signalType: Array<SignalType> | SignalType): MethodDecorator;

Parameters

• signalType - specific signal type or array of signal types to be handled by decorated method

Throws

• TypeError : no signal type parameter(s) present
• TypeError : decorated method does not belong to ContextManager class

Parameters

• Should be used to mark some service methods as signal event handlers
• Signal handlers are used to notify every service at once about something
• Same approach as with 'reducer-action' but without functional data stores

Usage

If services need to handle some global events that would require manual action calls each time, signals can be used.
Also useful when one context service requires reaction from others.
For example, connection manager can notify other services about state change or network issues.

enum EGlobalSignal {
  CONNECTION_STATE_CHANGE = "CONNECTION_STATE_CHANGE"
}

export class NetworkManager extends ContextManager {
  public onConnectionStateChanged(connectionState: boolean): void {
    this.emitSignal({ type: "CONNECTION_STATE_CHANGE", data: connectionState });
  }
}

Current implementation of 'onConnectionStateChanged' emits signal when being called. Emitted signal contains type and current connection state information.

Manager that handles signal can look like this:

type TConnectionStateSignal = SignalEvent<EGlobalSignal.CONNECTION_STATE_CHANGE, boolean>;

export class HandlerManager extends ContextManager {
  @OnSignal(EGlobalSignal.CONNECTION_STATE_CHANGE)
  public onConnectionStateChanged(signalEvent: TConnectionStateSignal): string {
    if (signalEvent.data) {
      log.info("Network state changed to connected:", signalEvent);
    } else {
      log.info("Network state changed to disconnected:", signalEvent);
    }
  }
}

Every time something emits 'CONNECTION_STATE_CHANGE' event, HandlerManager will react with strictly declared logic.