Using @query with LitElement and Typescript

Question

I'm trying to do this:

@query('#gist')
gist: HTMLIFrameElement;

And the typescript linting says:

Property 'gist' has no initializer and is not definitely assigned in the constructor.

How do we clear this?

user_3861822 · Answer

You can use a ! after the property name. This tells Typescript that the value will be set.

@query('#gist')
gist!: HTMLIFrameElement|null;