xref: /docs/en/application-dev/basic-services/common-event/common-event-publish.md

# Publishing Common Events


## When to Use

You can use [publish()](../../reference/apis-basic-services-kit/js-apis-commonEventManager.md#commoneventmanagerpublish) to publish a custom common event, which can carry data for subscribers to parse and process.

> **NOTE**
> Subscribers can receive sticky common events that have been sent. However, they must subscribe to common events of other types before receiving them. For details about subscription, see [Subscribing to Common Events](common-event-subscription.md).


## Available APIs

For details about the APIs, see [API Reference](../../reference/apis-basic-services-kit/js-apis-commonEventManager.md#commoneventmanagerpublish).

| API                                                      | Description                    |
| ------------------------------------------------------------ | ---------------------------- |
| publish(event: string, callback: AsyncCallback) | Publishes a common event.              |
| publish(event: string, options: [CommonEventPublishData](../../reference/apis-basic-services-kit/js-apis-inner-commonEvent-commonEventPublishData.md), callback: AsyncCallback) | Publishes a common event with given attributes.|


## Publishing a Common Event That Does Not Carry Information

Common events that do not carry information can be published only as unordered common events.

1. Import the **commonEventManager** module.
   
   ```ts
   import Base from '@ohos.base';
   import commonEventManager from '@ohos.commonEventManager';
   import promptAction from '@ohos.promptAction';
   import hilog from '@ohos.hilog';

   const TAG: string = 'ProcessModel';
   const DOMAIN_NUMBER: number = 0xFF00;
   ```

2. Pass in the common event name and callback, and publish the event.
   
   ```ts
   // Publish the common event. Replace the event field with the actual event name.
   commonEventManager.publish('event', (err: Base.BusinessError) => {
     if (err) {
       hilog.info(DOMAIN_NUMBER, TAG, `PublishCallBack err = ${JSON.stringify(err)}`);
     } else {
       //...
       hilog.info(DOMAIN_NUMBER, TAG, `Publish success`);
     }
   });
   ```


## Publishing a Common Event That Carries Information

Common events that carry information can be published as unordered, ordered, and sticky common events, which are specified by the **isOrdered** and **isSticky** fields of [CommonEventPublishData](../../reference/apis-basic-services-kit/js-apis-inner-commonEvent-commonEventPublishData.md).

1. Import the **commonEventManager** module.
   
   ```ts
   import Base from '@ohos.base';
   import commonEventManager from '@ohos.commonEventManager';
   import hilog from '@ohos.hilog';

   const TAG: string = 'ProcessModel';
   const DOMAIN_NUMBER: number = 0xFF00;
   ```

2. Create the public event information to be released.
   
   ```ts
   // Attributes of a common event.
   let options: commonEventManager.CommonEventPublishData = {
     code: 1, // Result code of the common event.
     data: 'initial data', // Initial data of the common event.
   };
   ```

3. Pass in the common event name, attributes of the common event, and callback, and publish the event.
   
   ```ts
   // Publish the common event. Replace the event field with the actual event name.
   commonEventManager.publish('event', options, (err: Base.BusinessError) => {
     if (err) {
       hilog.error(DOMAIN_NUMBER, TAG, 'PublishCallBack err = ' + JSON.stringify(err));
     } else {
       //...
       hilog.info(DOMAIN_NUMBER, TAG, 'Publish success');
     }
   });
   ```