import { Meta } from "@storybook/addon-docs";

<Meta title="Component Library/Async Actions/Standalone/Documentation" />

# Standalone Async Actions

These directives should be used when building a standalone button that triggers a long running task in the background,
eg. Refresh buttons. For non-submit buttons that are associated with forms see [Async Actions In Forms](?path=/story/component-library-async-actions-in-forms-documentation--page).

## Usage

Adding async actions to standalone buttons requires the following 2 steps

### 1. Add a handler to your `Component`

A handler is a function that returns a promise or an observable. Functions that return `void` are also supported which is
useful because `return;` can be used to abort an action.

**NOTE:** Defining the handlers as arrow-functions assigned to variables is mandatory if the handler needs access to the parent
component using the variable `this`.

**NOTE:** Handlers do not need to check if any previous requests have finished because the directives have built in protection against
users attempting to trigger new actions before the previous ones have finished.

#### Example using promises

```ts
@Component({...})
class PromiseExampleComponent {
  handler = async () => {
    await this.apiService.post(/* ... */);
  };
}
```

#### Example using observables

```ts
@Component({...})
class Component {
  handler = () => {
    return this.apiService.post$(/* ... */);
  };
}
```

### 2. Add directive to the DOM element

Add the `bitAction` directive and supply the handler defined in step 1.

**NOTE:** The `directive` is defined using the input syntax: `[input]="handler"`.
This is different from how click handlers are usually defined with the output syntax `(click)="handler()"`.

**NOTE:** `[bitAction]` is used instead of `(click)`. Using both is not supported.

```html
<button bitButton [bitAction]="handler">Do action</button>

<button bitIconButton="bwi-trash" [bitAction]="handler"></button>`;
```
