Testing: Abstract classes are not allowed in the Providers section of the Angular dependency injection framework

The service class for testing:

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

@Injectable({
    providedIn: 'root',})export abstract class HttpErrorHandler{
    constructor(){}
    abstract handleError(
      ): void;
}

@Injectable({
    providedIn: 'root',})export class UnKnownHandler {
    handleError(){
        console.log('UnknownHandler works'); }}@Injectable({
    providedIn: 'root',})export class BadGatewayHandler {
    handleError(){
        console.log('BadGatewayHandlers works'); }}Copy the code

Because abstract class can’t be instantiated, the above definition gets an error message:

Cannot assign an abstract constructor type to a non-abstract constructor type.

Solutions:

The runtime is injected with an array of HttpErrorHandler subclasses:

More of Jerry’s original articles can be found in “Wang Zixi” :