---
Title: Extension Service
Added: v3.0.0
Status: Experimental
Last reviewed: 2019-03-19
---

# [Extension Service](../../../lib/extensions/src/lib/services/extension.service.ts "Defined in extension.service.ts")

Manages and runs basic extension functionality.

## Class members

### Methods

*   **evaluateRule**(ruleId: `string`, context?: [`RuleContext`](../../../lib/extensions/src/lib/config/rule.extensions.ts)): `boolean`<br/>
    Evaluates a rule.
    *   *ruleId:* `string`  - ID of the rule to evaluate
    *   *context:* [`RuleContext`](../../../lib/extensions/src/lib/config/rule.extensions.ts)  - (Optional) Custom rule execution context.
    *   **Returns** `boolean` - True if the rule passed, false otherwise
*   **getActionById**(id: `string`): [`ActionRef`](../../../lib/extensions/src/lib/config/action.extensions.ts)<br/>
    Retrieves an action using its ID value.
    *   *id:* `string`  - The ID value to look for
    *   **Returns** [`ActionRef`](../../../lib/extensions/src/lib/config/action.extensions.ts) - Action or null if not found
*   **getAuthGuards**(ids: `string[]`): `Array<Type<Function>>`<br/>
    Retrieves one or more auth guards using an array of ID values.
    *   *ids:* `string[]`  - Array of ID value to look for
    *   **Returns** `Array<Type<Function>>` - Array of auth guards or empty array if none were found
*   **getComponentById**(id: `string`): `Type<>`<br/>
    Retrieves a registered [extension component](../../../lib/extensions/src/lib/services/component-register.service.ts) using its ID value.
    *   *id:* `string`  - The ID value to look for
    *   **Returns** `Type<>` - The component or null if not found
*   **getElements**(key: `string`, fallback: `Array<>` = `[]`): `Array<>`<br/>

    *   *key:* `string`  -
    *   *fallback:* `Array<>`  -
    *   **Returns** `Array<>` -
*   **getEvaluator**(key: `string`): [`RuleEvaluator`](../../../lib/extensions/src/lib/config/rule.extensions.ts)<br/>
    Retrieves a [RuleEvaluator](../../../lib/extensions/src/lib/config/rule.extensions.ts) function using its key name.
    *   *key:* `string`  - Key name to look for
    *   **Returns** [`RuleEvaluator`](../../../lib/extensions/src/lib/config/rule.extensions.ts) - [RuleEvaluator](../../../lib/extensions/src/lib/config/rule.extensions.ts) or null if not found
*   **getFeature**(key: `string`): `any[]`<br/>
    Gets features by key.
    *   *key:* `string`  - Key string, using dot notation
    *   **Returns** `any[]` - Features array found by key
*   **getRouteById**(id: `string`): [`RouteRef`](../../../lib/extensions/src/lib/config/routing.extensions.ts)<br/>
    Retrieves a route using its ID value.
    *   *id:* `string`  - The ID value to look for
    *   **Returns** [`RouteRef`](../../../lib/extensions/src/lib/config/routing.extensions.ts) - The route or null if not found
*   **getRuleById**(id: `string`): [`RuleRef`](../../../lib/extensions/src/lib/config/rule.extensions.ts)<br/>
    Retrieves a rule using its ID value.
    *   *id:* `string`  - The ID value to look for
    *   **Returns** [`RuleRef`](../../../lib/extensions/src/lib/config/rule.extensions.ts) - The rule or null if not found
*   **load**(): [`Promise`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises)`<`[`ExtensionConfig`](../../../lib/extensions/src/lib/config/extension.config.ts)`>`<br/>
    Loads and registers an extension config file and plugins (specified by path properties).
    *   **Returns** [`Promise`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises)`<`[`ExtensionConfig`](../../../lib/extensions/src/lib/config/extension.config.ts)`>` - The loaded config data
*   **runExpression**(value: `string|Function`, context?: `any`): `Function`<br/>
    Runs a lightweight expression stored in a string.
    *   *value:* `string|Function`  - String containing the expression or literal value
    *   *context:* `any`  - (Optional) Parameter object for the expression with details of app state
    *   **Returns** `Function` - Result of evaluated expression, if found, or the literal value otherwise
*   **setAuthGuards**(values: `Function`)<br/>
    Adds one or more new auth guards to the existing set.
    *   *values:* `Function`  - The new auth guards to add
*   **setComponents**(values: `Function`)<br/>
    Adds one or more new components to the existing set.
    *   *values:* `Function`  - The new components to add
*   **setEvaluators**(values: `Function`)<br/>
    Adds one or more new rule evaluators to the existing set.
    *   *values:* `Function`  - The new evaluators to add
*   **setup**(config: [`ExtensionConfig`](../../../lib/extensions/src/lib/config/extension.config.ts))<br/>
    Registers extensions from a config object.
    *   *config:* [`ExtensionConfig`](../../../lib/extensions/src/lib/config/extension.config.ts)  - Object with config data

## Details

Use the methods of this service to add extensibility features to your app. You can find further
details in the [App extensions](../../user-guide/app-extensions.md) page.