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name: umbraco-controllers description: Understand and create controllers in Umbraco backoffice (foundational concept) version: 1.0.0 location: managed allowed-tools: Read, Write, Edit, WebFetch

Umbraco Controllers

What is it?

Controllers are separate classes that contain or reuse logic across elements while maintaining connection to an element's lifecycle. A Controller is assigned to a Host Element and supports lifecycle methods (hostConnected, hostDisconnected, destroy) for managing side effects, timers, subscriptions, and cleanup. Controllers can host other controllers, enabling composition and reuse of functionality.

Documentation

Always fetch the latest docs before implementing:

• Main docs: https://docs.umbraco.com/umbraco-cms/customizing/foundation/umbraco-controller
• Write Custom Controller: https://docs.umbraco.com/umbraco-cms/customizing/foundation/umbraco-controller/write-your-own-controller
• Foundation: https://docs.umbraco.com/umbraco-cms/customizing/foundation

Workflow

1. Fetch docs - Use WebFetch on the URLs above
2. Ask questions - Need custom controller? What lifecycle events? What cleanup needed?
3. Generate code - Implement controller extending UmbControllerBase based on latest docs
4. Explain - Show what was created and how to host it

Minimal Examples

Basic Custom Controller

Copyimport { UmbControllerBase } from '@umbraco-cms/backoffice/class-api';
import type { UmbControllerHost } from '@umbraco-cms/backoffice/controller-api';

export class MyController extends UmbControllerBase {
  constructor(host: UmbControllerHost) {
    super(host);
    // Auto-registers with host
  }

  override hostConnected() {
    super.hostConnected();
    console.log('Controller connected!');
  }

  override hostDisconnected() {
    super.hostDisconnected();
    console.log('Controller disconnected!');
  }

  override destroy() {
    super.destroy();
    console.log('Controller destroyed!');
  }
}

Timer Controller Example

Copyimport { UmbControllerBase } from '@umbraco-cms/backoffice/class-api';
import type { UmbControllerHost } from '@umbraco-cms/backoffice/controller-api';

export class TimerController extends UmbControllerBase {
  #timer?: number;
  #secondsAlive = 0;

  constructor(host: UmbControllerHost) {
    super(host);
  }

  override hostConnected() {
    super.hostConnected();
    // Start timer when element connects to DOM
    this.#timer = window.setInterval(this.#onInterval, 1000);
  }

  override hostDisconnected() {
    super.hostDisconnected();
    // Clean up timer when element disconnects
    if (this.#timer) {
      clearInterval(this.#timer);
    }
  }

  #onInterval = () => {
    this.#secondsAlive++;
    console.log(`Controller active for ${this.#secondsAlive} seconds`);
  };

  override destroy() {
    super.destroy();
    if (this.#timer) {
      clearInterval(this.#timer);
    }
  }

  getSecondsAlive(): number {
    return this.#secondsAlive;
  }
}

Hosting a Controller in Element

Copyimport { UmbLitElement } from '@umbraco-cms/backoffice/lit-element';
import { TimerController } from './timer-controller.js';

export class MyElement extends UmbLitElement {
  #timerController = new TimerController(this);

  render() {
    return html`
      <div>
        Active for: ${this.#timerController.getSecondsAlive()}s
      </div>
    `;
  }
}

Manual Registration (Not Recommended)

Copyexport class MyManualController {
  #host: UmbControllerHost;

  constructor(host: UmbControllerHost) {
    this.#host = host;
    // Manual registration required
    this.#host.addUmbController(this);
  }

  hostConnected() {
    console.log('Connected');
  }

  destroy() {
    // Manual deregistration required
    this.#host.removeUmbController(this);
  }
}

Controller with Context Access

Copyimport { UmbControllerBase } from '@umbraco-cms/backoffice/class-api';
import { UMB_NOTIFICATION_CONTEXT } from '@umbraco-cms/backoffice/notification';

export class NotificationController extends UmbControllerBase {
  async showSuccess(message: string) {
    // Controllers can access contexts via getContext
    const context = await this.getContext(UMB_NOTIFICATION_CONTEXT);
    context?.peek('positive', { data: { message } });
  }
}

Key Concepts

Host Element: Web component that hosts the controller (all Umbraco Elements can be hosts)

Lifecycle Methods:

• hostConnected() - Called when host element connects to DOM
• hostDisconnected() - Called when host element disconnects from DOM
• destroy() - Called when controller is permanently destroyed

Auto-Registration: Extending UmbControllerBase automatically registers/deregisters

Controller Composition: Controllers can host other controllers

Context Access: Controllers can consume contexts via getContext() and consumeContext()

Use Cases:

• Managing subscriptions and cleanup
• Handling timers and intervals
• Coordinating side effects
• Reusing logic across multiple elements
• Managing API calls and data fetching

API Calls: When making API calls from controllers, NEVER use raw fetch(). Always use a generated OpenAPI client configured with Umbraco's auth context. See the umbraco-openapi-client skill for setup.

That's it! Always fetch fresh docs, keep examples minimal, generate complete working code.