“无法解析服务的所有参数：（？）”当我尝试在Angular 10中使用来自library的服务时

Question

在我的库中，我有一个带有以下代码的服务：

import { Inject, Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { DataInjectorModule } from '../../data-injector.module';

// @dynamic
@Injectable()
export class RemoteDataService<T> {
  @Inject('env') private environment: any = {};
  public type: new () => T;
  
  constructor(
    model: T,
  ) {
    this.http = DataInjectorModule.InjectorInstance.get(HttpClient);
  }

  // ...
}

data-injector.module（现有原因只是避免循环依赖）：

import { NgModule, Injector } from '@angular/core';

// @dynamic
@NgModule({
  declarations: [],
  imports: [],
  providers: [],
  exports: [],
})
export class DataInjectorModule {
  static InjectorInstance: Injector;

  constructor(injector: Injector) {
    DataInjectorModule.InjectorInstance = injector;
  }

}

import { ModuleWithProviders } from '@angular/compiler/src/core';
import { NgModule, Injector } from '@angular/core';
import { DataInjectorModule } from './data-injector.module';
import { RemoteDataService } from './services/remote-data/remote-data.service';

// @dynamic
@NgModule({
  declarations: [],
  imports: [
    DataInjectorModule,
  ],
  providers: [],
  exports: [],
})
export class DataCoreModule {
  static InjectorInstance: Injector;

  constructor(injector: Injector) {
    DataCoreModule.InjectorInstance = injector;
  }

  public static forRoot(environment: any): ModuleWithProviders {
    return {
      ngModule: DataCoreModule,
      providers: [
        RemoteDataService,
        { provide: 'env', useValue: environment }
      ]
    };
  }
}

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { DataCoreModule } from 'data-core';

import { AppRoutingModule } from './app-routing.module';
import { environment } from 'src/environments/environment';

import { AppComponent } from './app.component';

@NgModule({
  declarations: [
    AppComponent,
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    DdataCoreModule.forRoot(environment),
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Error: Can't resolve all parameters for RemoteDataService: (?).
    at getUndecoratedInjectableFactory (core.js:11338)
    at injectableDefOrInjectorDefFactory (core.js:11328)
    at providerToFactory (core.js:11371)
    at providerToRecord (core.js:11358)
    at R3Injector.processProvider (core.js:11256)
    at core.js:11230
    at core.js:1146
    at Array.forEach (<anonymous>)
    at deepForEach (core.js:1146)
    at R3Injector.processInjectorType (core.js:11230)

Answer 1

错误：无法解析RemoteDataService的所有参数：（？）

错误说明了一切。Angular无法解析RemoteDataService中的所有构造函数参数。实例化此服务时，它需要所需的参数。

您可以通过InjectionToken提供所需的依赖项，详细信息请参见此答案。

import { Component, Inject } from "@angular/core";
import { RemoteDataService } from "./custom/remote-data.service";

export class A {}

export class B {}

@Component({
  selector: "my-app",
  templateUrl: "./app.component.html",
  styleUrls: ["./app.component.css"],
  providers: [
    { provide: "env", useValue: {} },
    {
      provide: "ARemoteDataService",
      useFactory: () => new RemoteDataService<A>(new A())
    },
    {
      provide: "BRemoteDataService",
      useFactory: () => new RemoteDataService<B>(new B())
    }
  ]
})
export class AppComponent {
  constructor(
    @Inject("ARemoteDataService")
    private aRemoteDataService: RemoteDataService<A>,
    @Inject("BRemoteDataService")
    private bRemoteDataService: RemoteDataService<B>
  ) {}
}

// @Inject('env') private environment: any = {};
constructor(model: T) {
this.environment = DataInjectorModule.InjectorInstance.get("env");

}