NullInjectorError with InjectionToken ToastConfig

Introduction

The purpose of this document is to provide an explanation and solution for the NullInjectorError that occurs due to the absence of a provider for the InjectionToken ToastConfig.

Problem Description

When running your application, you encountered the following error message:

NullInjectorError: R3InjectorError(DynamicTestModule)[AdminTestCentersComponent -> ToastrService -> InjectionToken ToastConfig -> InjectionToken ToastConfig]: NullInjectorError: No provider for InjectionToken ToastConfig!

This error occurs when the Angular dependency injector cannot find a provider for the InjectionToken ToastConfig. The InjectionToken is a special type in Angular that allows us to create a unique token for injecting dependencies. In this case, the ToastConfig is not being correctly provided.

Solution

To resolve this issue, you need to ensure that the ToastConfig is properly provided in your application.

Here are the steps to follow:

1. Open the file where the AdminTestCentersComponent is defined.

2. Check if there is a providers array defined within the @Component decorator. This array is used to specify the providers for the component.

3. Add the ToastrService and ToastConfig to the providers array. This ensures that the required dependencies are provided for the AdminTestCentersComponent. Your code should look like this:

   import { Component } from '@angular/core';
   import { ToastrService, InjectionToken } from 'toastr'; // Replace 'toastr' with the actual library you're using
   
   export const ToastConfig = new InjectionToken<any>('ToastConfig');
   
   @Component({
     // Component metadata
     providers: [ToastrService, { provide: ToastConfig, useValue: yourToastConfigObject }]
   })
   export class AdminTestCentersComponent {
     // Component code
   }
   

   Note: Replace 'toastr' with the actual library you are using for displaying toast notifications. Also, ensure you have defined the yourToastConfigObject variable to hold the configuration for the toast.

4. Save the file and rebuild your application.

By correctly providing the ToastrService and ToastConfig, the Angular dependency injector will be able to resolve the dependencies and the NullInjectorError should no longer occur.

Conclusion

The NullInjectorError in relation to the InjectionToken ToastConfig can be resolved by providing the necessary dependencies for the affected component. By following the provided steps, you should be able to overcome this error and continue your development without any issues.