我已经在Angular中创建了一个 Singleton 服务,该服务会在应用程序启动之前进行API调用。它可以在第一个加载的页面上运行,但是如果我导航到另一个页面,它会显示:
错误错误:未捕获(承诺):错误:StaticInjectorError(AppModule)[MyComponent-> MyService]: StaticInjectorError(平台:核心)[MyComponent-> MyService]: NullInjectorError:MyService没有提供程序!
我现在不知道为什么,因为该服务被注入到两个组件中,并且可用于第一个组件。
我的app.module.ts
:
providers: [
MyService, {
provide: APP_INITIALIZER,
useFactory: (myService: MyService) => function () { return myService.load() },
deps: [MyService],
multi: true
}]
我的my.service.ts
:
@Injectable()
export class MyService {
...
}
两个组件中的导入:
constructor(private myService: MyService) { }
有人可以指导我解决此问题吗?
答案 0 :(得分:2)
我尝试复制您的问题,但是它对我有用。 请检查此代码。 https://stackblitz.com/edit/angular-palz6c
import { NgModule, APP_INITIALIZER } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { HelloComponent } from './hello.component';
import { MyServiceService } from './my-service.service';
import { TestComponent } from './test/test.component';
@NgModule({
imports: [ BrowserModule, FormsModule ],
declarations: [ AppComponent, HelloComponent, TestComponent ],
bootstrap: [ AppComponent ],
providers: [MyServiceService, {
provide: APP_INITIALIZER,
useFactory: (myService: MyServiceService) => function () { return myService.load() },
deps: [MyServiceService],
multi: true
}]
})
export class AppModule { }
服务
import { Injectable } from '@angular/core';
@Injectable()
export class MyServiceService {
constructor() { }
load() {
// return new Promise<void>((resolve, reject) => {
// console.log("AppInitService.init() called");
// ////do your initialisation stuff here
// setTimeout(() => {
// console.log('AppInitService Finished');
// resolve();
// }, 6000);
// });
console.log('AppInitService Finished');
}
test(val){
console.log('test' + '-' + val);
}
}
组件:
import { Component, OnInit } from '@angular/core';
import { MyServiceService } from '../my-service.service'
@Component({
selector: 'app-test',
templateUrl: './test.component.html',
styleUrls: ['./test.component.css']
})
export class TestComponent implements OnInit {
constructor(private service: MyServiceService) {
console.log(this.service.test('Test Component'));
}
ngOnInit() {
}
}
请让我知道我是否在这里丢失任何东西。
答案 1 :(得分:0)
尝试添加到my.service.ts:
@Injectable({providedin 'root'})