Angular 8 在初始化之前无法访问“PlanningModule”

Question

我正在使用themeforest 的apex 主题。我正在尝试访问该页面：/planning但是，控制台显示错误：

core.js:6014 ERROR Error: Uncaught (in promise): ReferenceError: Cannot access 'PlanningModule' before initialization
ReferenceError: Cannot access 'PlanningModule' before initialization
    at Module.PlanningModule (planning.component.ts:12)
    at planning-layout.routes.ts:6

我没有组件或模块的双重初始化。中只有初始化是服务app.module。为什么我会收到这个错误，我该如何解决？

App-routing.module.ts：

{
    path: 'planning',
    component: FullLayoutComponent,
    children: Planning_ROUTES,
    canActivate: [AuthGuard],
},

规划.module.ts：

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import {PlanningComponent} from './planning.component';
import {FormsModule} from '@angular/forms';
import {DragulaModule} from 'ng2-dragula';
import {Ng2SmartTableModule} from 'ng2-smart-table';
import {NgSelectModule} from '@ng-select/ng-select';
import {PlanningRoutingModule} from './planning-routing.module';


@NgModule({
  declarations: [
    PlanningComponent
  ],
  imports: [
    CommonModule,
    FormsModule,
    DragulaModule.forRoot(),
    Ng2SmartTableModule,
    NgSelectModule,
    PlanningRoutingModule
  ]
})
export class PlanningModule { }

规划-routing.module.ts：

import {NgModule} from '@angular/core';
import {RouterModule, Routes} from '@angular/router';

import {PlanningComponent} from './planning.component';


const routes: Routes = [
  {
    path: '',
    component: PlanningComponent,
  },
];

@NgModule({
  imports: [RouterModule.forChild(routes)],
  exports: [RouterModule],
})
export class PlanningRoutingModule {
  constructor() {
    console.log('hier komt die(niet)');
  }
}

规划组件.ts：

import {Component, OnInit} from '@angular/core';
import {Router} from '@angular/router';
import {PlanningService} from './planning.service';

@Component({
  selector: 'app-planning',
  templateUrl: './planning.component.html',
  styleUrls: ['./planning.component.scss'],
})
export class PlanningComponent implements OnInit {

  constructor(private router: Router,
    private planningService: PlanningService) {}

  ngOnInit(): void {}
}

规划-routes.ts：

import { Routes, RouterModule } from '@angular/router';

export const Planning_ROUTES: Routes = [
  {
    path: '',
    loadChildren: () => import('../../pages/planning/index/planning.module').then(m => m.PlanningModule)
  },
];

Answer 1

当 1 个或多个 Angular 模块之间存在循环依赖时，就会发生这种情况。我发现即使依赖是间接的，例如服务导入，也会发生这种情况。我假设这与初始化顺序有关。

例如 -

该组件依赖于另一个模块子目录中定义的服务 -

// declared in A_Module
export class A_Component implements OnInit {
//...
  constructor(
    private service: B_Service) {} // <-- dependency on B_Module??

}

// B_Module
@NgModule({
  imports: [
    CommonModule,
    A_Module // <-- dependency 
  ],
  exports: [],
  declarations: [...],
  providers: []
})
export class B_Module { }

// In B_Module sub-directory
@Injectable({providedIn: 'root'})
export class B_Service {}

为了解决这个问题，我Input()在A_Component. 一种选择可能是将服务移动到共享模块文件夹下。