Скачать или смотреть Resolving the router-outlet Error in Angular 12: A Guide for Developers

Struggling with the `router-outlet` is not a known element error in Angular 12? Follow our guide to find the solution and avoid common pitfalls!
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Resolving the router-outlet Error in Angular 12: A Guide for Developers

Upgrading your Angular application can sometimes introduce unexpected errors, especially when merging different versions. If you've recently upgraded from Angular 5 to Angular 12 and encountered the error message: error NG8001: 'router-outlet' is not a known element, you're not alone. This guide will explore the root cause of this issue and guide you step-by-step to a solution. We’ll also address an additional common error related to ngModel for a more comprehensive understanding.

Understanding the Problem

When you upgrade your Angular version, there are several changes in how modules and components interact. The error you are facing typically indicates that Angular cannot recognize a directive or component that is supposed to be available in the current context.

Router Module Error: The primary error, 'router-outlet is not a known element', suggests that the Angular RouterModule is not correctly set up in your application.

ngModel Error: Along with the router-outlet issue, you might also receive an error related to ngModel, specifically stating that it can't bind because it isn't recognized. This often indicates that the FormsModule hasn't been imported where it's required.

Step-by-Step Solution

Let’s break down the solution into clear sections:

1. Fixing the router-outlet Error

To resolve the router-outlet error, you need to ensure that the RouterModule is imported from your routing module, and not in your main application module (app.module.ts). Here’s what you must do:

Step 1: Open your app.module.ts file.

Step 2: Find the import { RouterModule } from '@ angular/router'; line.

Step 3: Remove RouterModule from the imports array. This is because you've already imported routing in your AppRoutingModule which is correctly integrated into your app.

Your app.module.ts should look like this after the modification:

[[See Video to Reveal this Text or Code Snippet]]

2. Addressing the ngModel Issue

Next, let's tackle the ngModel issue. This error usually appears when the FormsModule hasn't been properly imported into the component that relies on it.

Step 1: Identify the component that uses the ngModel directive (likely in any of your forms or components using textareas).

Step 2: In that component's *.component.ts file, import FormsModule.

For instance, here is how the import should look:

[[See Video to Reveal this Text or Code Snippet]]

3. Reinstall Third-Party Modules

Given that you mentioned issues with third-party modules like pdf-viewer, ensure that all your dependencies align with Angular 12 standards. You can reinstall them if necessary. Check the compatibility of each library with Angular 12 and update package.json as required.

Conclusion

Upgrading Angular can introduce various challenges, but by understanding the structure of your application and ensuring proper imports, you can resolve common errors like the router-outlet and ngModel issues. Remember to carefully manage your module dependencies, especially when utilizing third-party libraries, to maintain compatibility.

By following these steps, you should be able to address the errors and continue building your Angular application confidently. Happy coding!