
psantos
Modern Front-End Development for Rails, Second Edition: Chapter 3, Stimulus - elementToHideTarget is undefined (p 52)
On page 52, example code chapter_03/04/app/javascript/controllers/favorite_toggle_controller.ts
, which is:
import { Controller } from "@hotwired/stimulus";
export default class FavoriteToggleController extends Controller {
static targets = ["elementToHide"];
elementToHideTarget: HTMLElement;
toggle(): void {
this.elementToHideTarget.classList.toggle("hidden");
}
}
The way it is, will not work, since elementToHideTarget will always be undefined. To work I needed to make the following change:
import { Controller } from "@hotwired/stimulus";
export default class FavoriteToggleController extends Controller {
static targets = ["elementToHide"];
declare readonly elementToHideTarget: HTMLElement;
toggle(): void {
this.elementToHideTarget.classList.toggle("hidden");
}
}
I did the same change on page 55:
static values = { visible: Boolean };
declare visibleValue: boolean;
Note that this time I did not declare it as readonly
, since I am changing its value on flipState()
function.
Versions:
Ruby 3.1.2
Rails: 7.0.4
Gem stimulus-rails: 1.1.0
@hotwired/stimulus: 3.1.0
First Post!

noelrappin
Author of Modern Front-End Development for Rails
What error do you get, and are you working from the supplied code or building it up yourself?
The elementToHideTarget should be set by Stimulus, it shouldn’t be undefined…
Thanks,
Noel
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