Incorrect (classic component):

// app/components/user-card.js
import Component from '@ember/component';
import { computed } from '@ember/object';

export default Component.extend({
  tagName: 'div',
  classNames: ['user-card'],

  fullName: computed('user.{firstName,lastName}', function () {
    return `${this.user.firstName} ${this.user.lastName}`;
  }),

  didInsertElement() {
    this._super(...arguments);
    // Complex lifecycle management
  },
});