Is there a way to use $emit in boot function defintion?

[luzdealba]

This is related to the $emit on app extension forum post.

Essentially, is there a way to invoke the emit() function from within a boot file?

[TobyMosque]

https://v3-migration.vuejs.org/breaking-changes/events-api.html#_3-x-update
but u can use a third party event library like mitt:

first of all, u can write a dumb inject helper to use in your boots:

import { App, InjectionKey } from 'vue';
export function inject<T>(app: App, key: InjectionKey<T>): T {
  return app._context.provides[key as never] as T;
}

so, create a boot who register the emitter, this boot would be called before the boots who requires the emitter.

import { boot } from 'quasar/wrappers';
import { InjectionKey } from 'vue';
import mitt, { Emitter } from 'mitt';

type Events = {
  foo: string;
  bar?: number;
};

export const emitterKey: InjectionKey<Emitter<Events>> = Symbol('emitter-key');
export default boot(({ app }) => {
  const emitter: Emitter<Events> = mitt<Events>();
  app.provide(emitterKey, emitter);
});

in other boots:

import { emitterKey } from './emitter'
import { boot } from 'quasar/wrappers';
import { inject } from 'src/utils';

export default boot(({ app }) => {
  const emitter = inject(app, emitterKey)
  emitter.on('foo', function (val: string) {
    console.log(val)
  })
  emitter.on('bar', function (val: number | undefined) {
    console.log(val)
  })
});

so, in your components:

import { emitterKey } from 'src/boot/emitter'
import { defineComponent, inject } from 'vue';

export default defineComponent({
  setup () {
    const emitter = inject(emitterKey)
    emitter.on('foo', function (val: string) {
      console.log(val)
    })
    emitter.on('bar', function (val: number | undefined) {
      console.log(val)
    })
  }
})

[luzdealba]

@TobyMosque I never thanked you for your detailed answer 🙏

For the record, I ended up having a helper function that would get the emit function as a parameter, and then invoking the emitter from inside the helper (that is, in whichever context the helper was used).