angular - 如何修复 'No provider for service' 错误？

Question

我得到一个错误:

"Exception: Call to Node module failed with error: Error: Uncaught (in promise): Error: No provider for ServiceModuleService! Error: No provider for ServiceModuleService!"

这是一些代码。

app.module.shared.ts:

import { NgModule } from '@angular/core';
import { RouterModule } from '@angular/router';
import { AppComponent } from './components/app/app.component'
import { ServiceModuleListComponent } from './components/service-module-list/service-module-list.component';
import { HeaderComponent } from './components/shared/header/header.component';
import { ServiceModuleService } from './components/shared/service-module.service';
import { ServiceModuleComponent } from './components/service-module/service-module.component';

export const sharedConfig: NgModule = {
    bootstrap: [AppComponent],
    declarations: [
        AppComponent,
        ServiceModuleListComponent,
        HeaderComponent,
        ServiceModuleComponent
    ],
    imports: [
        RouterModule.forRoot([
            { path: '', redirectTo: 'servicemodulelist', pathMatch: 'full' },
            { path: 'servicemodulelist', component: ServiceModuleListComponent },
            { path: '**', redirectTo: 'servicemodulelist' }
        ])
    ],
    providers: [ServiceModuleService]
};

app.module.client.ts:

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule } from '@angular/forms';
import { HttpModule } from '@angular/http';
import { sharedConfig } from './app.module.shared';

@NgModule({
    bootstrap: sharedConfig.bootstrap,
    declarations: sharedConfig.declarations,
    imports: [
        BrowserModule,
        FormsModule,
        HttpModule,
        ...sharedConfig.imports
    ],
    providers: [
        { provide: 'ORIGIN_URL', useValue: location.origin },
        sharedConfig.providers
    ]
})
export class AppModule {
}

应用程序组件.ts

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

@Component({
    selector: 'app',
    templateUrl: './app.component.html',
    styleUrls: ['./app.component.css']
})
export class AppComponent {
}

服务模块.component.ts:

import { Component, Input } from '@angular/core';
import { ServiceModule } from '../shared/service-module.type';

@Component({
    selector: 'service-module',
    templateUrl: './service-module.component.html'
})
export class ServiceModuleComponent {
    @Input() serviceModule: ServiceModule

    constructor() {

    }
}

服务模块列表.component.ts:

import { Component, OnInit } from '@angular/core';
import { ServiceModule } from '../shared/service-module.type';
import { ServiceModuleService } from '../shared/service-module.service';
import { ServiceModuleComponent }from '../service-module/service-module.component';

@Component({
    selector: 'service-module-list',
    templateUrl: './service-module-list.component.html'
})
export class ServiceModuleListComponent implements OnInit {
    serviceModules: ServiceModule[];

    constructor(private serviceModuleService: ServiceModuleService) {
    }

    ngOnInit() {
        this.serviceModuleService.getServiceModuleItems()
            .then(serviceModuleItems => {
                this.serviceModules = serviceModuleItems;
            });
    }
}

服务模块.service.ts:

import { Injectable } from '@angular/core';
import { Http } from '@angular/http';
import 'rxjs/Rx';
import { ServiceModule } from './service-module.type';

@Injectable()
export class ServiceModuleService {
    constructor(private http: Http) { }

    getServiceModuleItems() {
        return this.http.get('api/ServiceModuleItems')
            .map(response => response.json() as ServiceModule[])
            .toPromise();
    }
}

服务模块.type.ts:

    export class ServiceModule {
    idx: number;
    applicationName: string;
    isActive: boolean;
    description: string;
}

基本上在这一点上，在启动时，应用程序必须显示我在 SQL 表上的条目列表，服务调用 API 来获取它，但现在我被错误消息困在了这个问题上。

Answer 1

我进一步研究了这个语法:

imports: [
    BrowserModule,
    FormsModule,
    HttpModule,
    ...sharedConfig.imports
],

这里的 '...' 是 JavaScript 扩展运算符。它确保在此处添加导入的内容而不是数组本身。我的一位同事是这样解释的:

imports: [
  a,
  b,
  c,
  sharedConfig.imports
]

你最终得到(将数组放入)

imports: [a, b, c, [what_shared_config_has]]

而不是你想要的(数组中的值)

imports: [a, b, c, what_shared_config_has]

所以这也需要有传播运算符:

providers: [
    { provide: 'ORIGIN_URL', useValue: location.origin },
    ...sharedConfig.providers
]