Extending Factories

Custom factories are regular subclasses of EventFactory.

The usual shape is simple:

• add a static constructor like create() or modify()
• start from blankEventTemplate(kind) or toEventTemplate(event)
• expose fluent instance methods that call this.chain(...)

What It Is

This is the pattern used throughout applesauce-core/factories and applesauce-common/factories.

import { blankEventTemplate, EventFactory } from "applesauce-core/factories";

class StatusFactory extends EventFactory<30315> {
  static create() {
    return new StatusFactory((resolve) => resolve(blankEventTemplate(30315)));
  }

  status(text: string) {
    return this.content(text);
  }
}

How To Use It

Start a new event

class StatusFactory extends EventFactory<30315> {
  static create() {
    return new StatusFactory((resolve) => resolve(blankEventTemplate(30315))).status("online");
  }

  status(text: string) {
    return this.content(text);
  }
}

const event = await StatusFactory.create().sign(signer);

When you add a static create() method, it should return a factory that already represents a valid event for that kind. Extra options are fine, but the base result should include the required fields and tags. The factories in packages/common/src/factories/comment.ts and packages/common/src/factories/live-stream.ts follow this pattern.

Modify an existing event

import { toEventTemplate } from "applesauce-core/factories";

static modify(event: KnownEvent<30315>) {
  return new StatusFactory((resolve) => resolve(toEventTemplate(event)));
}

Add reusable methods

import { addNameValueTag } from "applesauce-core/operations/tag/common";
import { modifyPublicTags } from "applesauce-core/operations/tags";

priority(level: "low" | "high") {
  return this.chain(modifyPublicTags(addNameValueTag(["priority", level])));
}

this.chain(...) takes event operations. If you want to reuse a tag operation, wrap it with modifyPublicTags(...) or modifyHiddenTags(...) first. For simple cases, you can also call this.modifyPublicTags(...), this.modifyHiddenTags(...), or this.modifyTags(...) directly from the factory method.

Integration

Custom factories use the same signer and chain model as built-in factories.

const draft = StatusFactory.create().priority("high").as(signer);
const signed = await draft.sign();

You can also build small inheritance layers for families of events. applesauce-common/factories/list.ts defines ListFactory plus user- and item-oriented subclasses. The relay-list factories follow the same pattern, see Relay Lists.

Best Practices

• Keep constructors small and fluent methods focused on one change
• Use blankEventTemplate() for new events and toEventTemplate() for edits
• Make create() return a valid event shape for that kind before optional customization
• Put shared logic in operations when more than one factory needs it
• Validate kinds in modify(event) before creating a subclass instance