angular-docs-cn/modules/@angular/core/src/di/provider.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {Type} from '../type';

/**
 * @whatItDoes Configures the {@link Injector} to return an instance of `Type` when `Type' is used
 * as token.
 * @howToUse
 * ```
 * @Injectable()
 * class MyService {}
 *
 * const provider: TypeProvider = MyService;
 * ```
 *
 * @description
 *
 * Create an instance by invoking the `new` operator and supplying additional arguments.
 * This form is a short form of `TypeProvider`;
 *
 * For more details, see the {@linkDocs guide/dependency-injection "Dependency Injection Guide"}.
 *
 * ### Example
 *
 * {@example core/di/ts/provider_spec.ts region='TypeProvider'}
 *
 * @stable
 */
export interface TypeProvider extends Type<any> {}

/**
 * @whatItDoes Configures the {@link Injector} to return a value for a token.
 * @howToUse
 * ```
 * const provider: ValueProvider = {provide: 'someToken', useValue: 'someValue'};
 * ```
 *
 * @description
 * For more details, see the {@linkDocs guide/dependency-injection "Dependency Injection Guide"}.
 *
 * ### Example
 *
 * {@example core/di/ts/provider_spec.ts region='ValueProvider'}
 *
 * @stable
 */
export interface ValueProvider {
  /**
   * An injection token. (Typically an instance of `Type` or `InjectionToken`, but can be `any`).
   */
  provide: any;

  /**
   * The value to inject.
   */
  useValue: any;

  /**
   * If true, than injector returns an array of instances. This is useful to allow multiple
   * providers spread across many files to provide configuration information to a common token.
   *
   * ### Example
   *
   * {@example core/di/ts/provider_spec.ts region='MultiProviderAspect'}
   */
  multi?: boolean;
}

/**
 * @whatItDoes Configures the {@link Injector} to return an instance of `useClass` for a token.
 * @howToUse
 * ```
 * @Injectable()
 * class MyService {}
 *
 * const provider: ClassProvider = {provide: 'someToken', useClass: MyService};
 * ```
 *
 * @description
 * For more details, see the {@linkDocs guide/dependency-injection "Dependency Injection Guide"}.
 *
 * ### Example
 *
 * {@example core/di/ts/provider_spec.ts region='ClassProvider'}
 *
 * Note that following two providers are not equal:
 * {@example core/di/ts/provider_spec.ts region='ClassProviderDifference'}
 *
 * @stable
 */
export interface ClassProvider {
  /**
   * An injection token. (Typically an instance of `Type` or `InjectionToken`, but can be `any`).
   */
  provide: any;

  /**
   * Class to instantiate for the `token`.
   */
  useClass: Type<any>;

  /**
   * If true, than injector returns an array of instances. This is useful to allow multiple
   * providers spread across many files to provide configuration information to a common token.
   *
   * ### Example
   *
   * {@example core/di/ts/provider_spec.ts region='MultiProviderAspect'}
   */
  multi?: boolean;
}

/**
 * @whatItDoes Configures the {@link Injector} to return a value of another `useExisting` token.
 * @howToUse
 * ```
 * const provider: ExistingProvider = {provide: 'someToken', useExisting: 'someOtherToken'};
 * ```
 *
 * @description
 * For more details, see the {@linkDocs guide/dependency-injection "Dependency Injection Guide"}.
 *
 * ### Example
 *
 * {@example core/di/ts/provider_spec.ts region='ExistingProvider'}
 *
 * @stable
 */
export interface ExistingProvider {
  /**
   * An injection token. (Typically an instance of `Type` or `InjectionToken`, but can be `any`).
   */
  provide: any;

  /**
   * Existing `token` to return. (equivalent to `injector.get(useExisting)`)
   */
  useExisting: any;

  /**
   * If true, than injector returns an array of instances. This is useful to allow multiple
   * providers spread across many files to provide configuration information to a common token.
   *
   * ### Example
   *
   * {@example core/di/ts/provider_spec.ts region='MultiProviderAspect'}
   */
  multi?: boolean;
}

/**
 * @whatItDoes Configures the {@link Injector} to return a value by invoking a `useFactory`
 * function.
 * @howToUse
 * ```
 * function serviceFactory() { ... }
 *
 * const provider: FactoryProvider = {provide: 'someToken', useFactory: serviceFactory, deps: []};
 * ```
 *
 * @description
 * For more details, see the {@linkDocs guide/dependency-injection "Dependency Injection Guide"}.
 *
 * ### Example
 *
 * {@example core/di/ts/provider_spec.ts region='FactoryProvider'}
 *
 * Dependencies can also be marked as optional:
 * {@example core/di/ts/provider_spec.ts region='FactoryProviderOptionalDeps'}
 *
 * @stable
 */
export interface FactoryProvider {
  /**
   * An injection token. (Typically an instance of `Type` or `InjectionToken`, but can be `any`).
   */
  provide: any;

  /**
   * A function to invoke to create a value for this `token`. The function is invoked with
   * resolved values of `token`s in the `deps` field.
   */
  useFactory: Function;

  /**
   * A list of `token`s which need to be resolved by the injector. The list of values is than
   * used as arguments to the `useFactory` function.
   */
  deps?: any[];

  /**
   * If true, than injector returns an array of instances. This is useful to allow multiple
   * providers spread across many files to provide configuration information to a common token.
   *
   * ### Example
   *
   * {@example core/di/ts/provider_spec.ts region='MultiProviderAspect'}
   */
  multi?: boolean;
}

/**
 * @whatItDoes Describes how the {@link Injector} should be configured.
 * @howToUse
 * See {@link TypeProvider}, {@link ValueProvider}, {@link ClassProvider}, {@link ExistingProvider},
 * {@link FactoryProvider}.
 *
 * @description
 * For more details, see the {@linkDocs guide/dependency-injection "Dependency Injection Guide"}.
 *
 * @stable
 */
export type Provider =
    TypeProvider | ValueProvider | ClassProvider | ExistingProvider | FactoryProvider | any[];