How should you use a custom pipe within an Angular template?

Using a custom pipe within an Angular template is accomplished by employing the custom pipe name along with the pipe syntax. This syntax consists of the expression followed by the pipe symbol (|) and the name of the custom pipe. This allows data transformation to be seamlessly integrated into the template, making the code cleaner and more readable.

For example, if you have created a custom pipe named "customSortPipe", you would use it in your template like this:

<div *ngFor="let item of items | customSortPipe"></div>

This method is not only straightforward but also aligns with Angular's design principles, where pipes act as a way to transform data dynamically based on the context provided by the component.

The other methods suggested do not align with Angular's templating architecture. Directly calling the pipe function would bypass the Angular change detection mechanism and be outside of the intended usage within templates. Including the pipe in a service does not provide the necessary interface for the template to utilize it correctly. Declaring it in a router module would not serve the purpose either, as pipes need to be used within templates and not just declared in routing contexts. Thus, leveraging the custom pipe with the correct syntax is the appropriate approach.