Question

在我的Angular应用程序引导之前，我正在使用APP_INITIALIZER令牌在页面加载上执行某些操作。我用于该逻辑的服务取决于我CoreModule中的其他服务。

我知道这个错误正在发生，因为我正在将AuthService注入我的AppService，但是我不明白为什么这应该重要。 AuthService不会注入AppService，那么它是如何循环依赖的呢？

这是我的错误：

> Uncaught Error: Provider parse errors: Cannot instantiate cyclic
> dependency! ApplicationRef ("[ERROR ->]"): in NgModule AppModule in
> ./AppModule@-1:-1 Cannot instantiate cyclic dependency! ApplicationRef
> ("[ERROR ->]"): in NgModule AppModule in ./AppModule@-1:-1
>     at NgModuleProviderAnalyzer.parse (compiler.js:19550)
>     at NgModuleCompiler.compile (compiler.js:20139)
>     at JitCompiler._compileModule (compiler.js:34437)
>     at eval (compiler.js:34368)
>     at Object.then (compiler.js:474)
>     at JitCompiler._compileModuleAndComponents (compiler.js:34366)
>     at JitCompiler.compileModuleAsync (compiler.js:34260)
>     at CompilerImpl.compileModuleAsync (platform-browser-dynamic.js:239)
>     at PlatformRef.bootstrapModule (core.js:5567)
>     at bootstrap (main.ts:13)

这是我的AppModule：

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

import { AppService, AppServiceFactory } from './app.service';
import { CoreModule } from 'core';

@NgModule({
    imports: [
        // ...
        CoreModule,
        // ...
    ],
    providers: [
        AppService,
        {
            provide: APP_INITIALIZER,
            useFactory: AppServiceFactory,
            deps: [AppService],
            multi: true
        }
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule {}

以下是AppService：

import { Injectable } from '@angular/core';

import { finalize } from 'rxjs/operators';

import { AuthService } from 'core/services/auth/auth.service';

export function AppServiceFactory(appService: AppService): () => Promise<any> {
    return () => appService.doBeforeBootstrap();
}

@Injectable()
export class AppService {
    constructor(private authService: AuthService) {}

    doBeforeBootstrap(): Promise<any> {
        return new Promise(resolve => {
            this.authService.isLoggedIn().then((loggedIn: boolean) => {
                // If the user is logged in, resolve (do nothing).
                if (loggedIn) {
                    return resolve();
                }

                // Otherwise, refresh the users token before resolving.
                this.authService.refreshToken().pipe(
                    finalize(() => resolve())
                ).subscribe();
            });
        });
    }
}

有人知道为什么会出现这样的错误吗？

修改（AuthService的依赖关系）：

constructor(
    private ref: ApplicationRef,
    private router: Router,
    private http: HttpClient,
    // Other custom services that are NOT imported into AppService...
) {}

Answer 1

您向APP_INITIALIZER提供依赖于AppService依赖于AuthService ApplicationRef的{{1}}的工厂，该ApplicationInitStatus取决于依赖于{APP_INITIALIZER的{{1}} var map = new google.maps.Map(mapWrapperElem, mapOptions); map.addListener("click",function(event){ // Do stuff }); 1}} ... et voila

请参阅第398页的https://github.com/angular/angular/blob/5.2.9/packages/core/src/application_init.ts和https://github.com/angular/angular/blob/5.2.9/packages/core/src/application_ref.ts

Angular 5 APP_INITIALIZER：提供程序解析错误：无法实例化循环依赖项

1 个答案: