# feathers-trigger

<p align="center">
  <img src="https://feathers-trigger.netlify.app/img/logo.svg" width="200">
</p>

> NOTE: This is the version for Feathers v5. For Feathers v4 use [feathers-trigger v0](https://github.com/fratzinger/feathers-trigger/tree/crow)

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## Documentation

For more information, please have a look at the docs: [https://feathers-trigger.netlify.app/](https://feathers-trigger.netlify.app/getting-started.html)

## Installation

```bash
npm i feathers-trigger
```

## Usage

Imagine you want to notify users when a `post` gets published.

How can this be done? In this example a `post` has a `publishedAt` property which shows when a `post` was published. A `post` with `publishedAt === null` means that the `post` is not published yet. A `post` can be created as a draft which is not published.

But how do you know when a `post` gets published? Sounds silly, but there are three possibilities:

- A `post` gets created with `publishedAt: { $ne: null }`.
- A `post` gets updated by **data** `publishedAt: { $ne: null }`, it had `publishedAt: null` before and the **result** really has `publishedAt: { $ne: null }`.
- A `post` gets patched by **data** `publishedAt: { $ne: null }`, it had `publishedAt: null` before and the **result** really has `publishedAt: { $ne: null }`.

How can this be accomplished?

1. Check `context.data` for `publishedAt: { $ne: null }` and if that's not true, the subscription is not true.
2. Check if the post in the database has `publishedAt === null` and therefore is not published yet. You need to check that in a `before` hook. If that's not true, the subscription is not true.
3. Check if the `context.result` really has `publishedAt: { $ne: null }` (maybe it's handled by another permission hook, or something). If that's not true, the subscription is not true.
4. If all three checks are true, run the `notify` function.

It's up to you how you define the `notify` action. For the example above the solution with `feathers-trigger` looks like the following:

```js
// posts.hooks.js
import { trigger } from "feathers-trigger";

const notifyPublished = trigger({
  conditionsData: { publishedAt: { $ne: null } },
  conditionsBefore: { publishedAt: null },
  conditionsResult: { publishedAt: { $ne: null } },
  action: ({ item }, context) => {
    return context.app.service("/notify").create(item);
  },
});

export default {
  before: {
    create: [notifyPublished],
    update: [notifyPublished],
    patch: [notifyPublished],
  },
  after: {
    create: [notifyPublished],
    update: [notifyPublished],
    patch: [notifyPublished],
  },
};
```

For more advanced examples, please have a look at the [docs](https://feathers-trigger.netlify.app/getting-started.html)

## Testing

Simply run `npm test` and all your tests in the `test/` directory will be run. It has full support for _Visual Studio Code_. You can use the debugger to set breakpoints.

## Help

For more information on all the things you can do, visit [FeathersJS](http://docs.feathersjs.com).

## License

Licensed under the [MIT license](LICENSE).