Tips for verifying the types of an Angular component template

I have a specific component that requires two inputs. I am using TypeScript and looking for a way to ensure that the second input is only provided if the first input is also provided.

For example:

export class MyTestClass implements Test{
  @Input() dog?: string;
  @Input() treat?: string; // Should only be able to exist if dog also exists
}

I attempted to create a generic interface for the component, as shown below:

interface Test<Dog extends string | undefined = string> {
  dog?: Dog;
  treat?: Dog extends string ? string : undefined
}

However, TypeScript does not raise any errors when the template is used incorrectly, like so:

<my-test-class [treat]="'not type-checked'">
</my-test-class>

Is there a method in Angular to enforce this relationship between inputs during compile-time rather than run-time?

Answer №1

To specify the element selector for the @Component decorator, you can use the selector property:

@Component({
 template: "...",
 style: "...",
 selector: `
  app-my-component[dog],
  app-my-component[dog][treat],
  app-my-component:not([treat])
 `
})
class MyComponent { }

In this code snippet, I'm leveraging the use of , for logical OR operations, [attr] to target elements with specific attributes, and the :not pseudo-selector to exclude scenarios where only the treat attribute is present.

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