electron-trpc-demo/packages/trpc/common/routers/user.ts

import { router, publicProcedure } from '../trpc';
import { observable } from '@trpc/server/observable';
import { EventEmitter } from 'events';
import { WindowManager } from 'main/modules/window-manager';

const ee = new EventEmitter();

export const userRouter = router({
  userList: publicProcedure.query(() => {
    // [..]
    ee.emit('greeting', `Greeted`)
    return [
      {
        id: 1,
        name: 'John Doe',
        windowsLength: WindowManager.getWindowsLength(),
      },
      {
        id: 2,
        name: 'Jane Doe',
        windowsLength: WindowManager.getWindowsLength(),
      },
    ];
  }),
  subscribeGreeting: publicProcedure.subscription(() => {
    return observable<{ text: string }>((emit) => {
      function onGreet(text: string) {
        emit.next({ text });
      }

      ee.on('greeting', onGreet);

      return () => {
        ee.off('greeting', onGreet);
      };
    });
  }),
});