问使用forRoot向模块提供具有依赖关系的角度传递服务

EN

import { Injector, ModuleWithProviders, NgModule, Optional, Provider, SkipSelf } from '@angular/core';
import { isFunction } from 'lodash';

export function resolveService(cfg: SharedConfig, inj: Injector): IncompleteService {
  const provider = cfg?.service;
  // if service is an angular provider, use Injector, otherwise return service instance as simple value
  const service = isFunction(service) ? inj.get(provider) : provider;
  return service;
}

/**
 * Service to be implemented from outside the module.
 */
@Injectable()
export abstract class IncompleteService {
  abstract strategyMethod();
}

// Optional: A config object is optional of course, but usually it fits the needs.
export interface SharedConfig {
  service: IncompleteService | Type<IncompleteService> | InjectionToken<IncompleteService>;
  // other config properties...
}

/*
 * Optional: If a Config interface is used, one might resolve the config itself 
 * using other dependencies (e.g. load JSON via HTTPClient). Hence an InjectionToken 
 * is necessary.
 */
export const SHARED_CONFIG = new InjectionToken<SharedConfig>('shared-config');

// Optional: If SharedConfig is resolved with dependencies, it must be provided itself.  
export type ModuleConfigProvider = ValueProvider | ClassProvider | ExistingProvider | FactoryProvider;

/**
 * One can provide the config as is, i.e. "{ service: MyService }" or resolved by 
 * injection, i.e.
 * { provide: SHARED_CONFIG: useFactory: myConfigFactory, deps: [DependentService1, DependentService2] }
 */
@NgModule({
  declarations: [],
  imports: []
})
export class SharedModule {
  static forRoot(config: SharedConfig | ModuleConfigProvider): ModuleWithProviders<SharedModule> {
    // dynamic (config is Provider) or simple (config is SharedConfig)
    return {
      ngModule: SharedModule,
      providers: [
        (config as ModuleConfigProvider).provide ? (config as Provider) : { provide: SHARED_CONFIG, useValue: config },
        { provide: IncompleteService, useFactory: resolveService, deps: [SHARED_CONFIG, Injector] },
        // ... provide additional things
      ],
    };
}


/**
 * In general not really useful, because usually an instance of IncompleteService
 * need other dependencies itself. Hence you cannot provide this instance without
 * creating it properly. But for the sake of completeness, it should work as well.
 */
@NgModule({
  declarations: [],
  imports: []
})
export class MostSimpleSharedModule {
  static forRoot(service: IncompleteService): ModuleWithProviders<SharedModule> {
    // dynamic (config is Provider) or simple (config is SharedConfig)
    return {
      ngModule: SharedModule,
      providers: [
        { provide: IncompleteService, useValue: service },
        // ... provide additional things
      ],
    };
}