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reactjstypescriptelectronipc

contextBridge.exposeInMainWorld and IPC with Typescript in Electron app: Cannot read property 'send' of undefined

I defined contextBridge ( https://www.electronjs.org/docs/all#contextbridge ) in preload.js as follows:

const {
  contextBridge,
  ipcRenderer
} = require("electron")

contextBridge.exposeInMainWorld(
  "api", {
      send: (channel, data) => {
          ipcRenderer.invoke(channel, data).catch(e => console.log(e))
      },
      receive: (channel, func) => {
        console.log("preload-receive called. args: ");
        ipcRenderer.on(channel, (event, ...args) => func(...args));
      },
      // https://www.electronjs.org/docs/all#ipcrenderersendtowebcontentsid-channel-args
      electronIpcSendTo: (window_id: string, channel: string, ...arg: any) => {
        ipcRenderer.sendTo(window_id, channel, arg);
      },
      // https://github.com/frederiksen/angular-electron-boilerplate/blob/master/src/preload
/preload.ts
      electronIpcSend: (channel: string, ...arg: any) => {
        ipcRenderer.send(channel, arg);
      },
      electronIpcSendSync: (channel: string, ...arg: any) => {
        return ipcRenderer.sendSync(channel, arg);
      },
      electronIpcOn: (channel: string, listener: (event: any, ...arg: any) => void) => {
        ipcRenderer.on(channel, listener);
      },
      electronIpcOnce: (channel: string, listener: (event: any, ...arg: any) => void) => {
        ipcRenderer.once(channel, listener);
      },
      electronIpcRemoveListener:  (channel: string, listener: (event: any, ...arg: any) => 
void) => {
        ipcRenderer.removeListener(channel, listener);
      },
      electronIpcRemoveAllListeners: (channel: string) => {
        ipcRenderer.removeAllListeners(channel);
      }
  }
)

I defined a global.ts :

export {}
declare global {
  interface Window {
    "api": {
      send: (channel: string, ...arg: any) => void;
      receive: (channel: string, func: (event: any, ...arg: any) => void) => void;
      // https://github.com/frederiksen/angular-electron-boilerplate/blob/master/src/preload
/preload.ts
      // https://www.electronjs.org/docs/all#ipcrenderersendtowebcontentsid-channel-args
      electronIpcSendTo: (window_id: string, channel: string, ...arg: any) => void;
      electronIpcSend: (channel: string, ...arg: any) => void;
      electronIpcOn: (channel: string, listener: (event: any, ...arg: any) => void) => void;
      electronIpcSendSync: (channel: string, ...arg: any) => void;
      electronIpcOnce: (channel: string, listener: (event: any, ...arg: any) => void) => 
void;
      electronIpcRemoveListener:  (channel: string, listener: (event: any, ...arg: any) =>
 void) => void;
      electronIpcRemoveAllListeners: (channel: string) => void;
    }
  }
}

and in the renderer process App.tsx I call window.api.send :

window.api.send('open-type-A-window', '');

The typescript compilation looks fine:

yarn run dev
yarn run v1.22.5 
$ yarn run tsc && rimraf dist && cross-env NODE_ENV=development webpack --watch --progress 
--color
$ tsc
95% emitting emit(node:18180) [DEP_WEBPACK_COMPILATION_ASSETS] DeprecationWarning:      
Compilation.assets will be frozen in future, all modifications are deprecated.

BREAKING CHANGE: No more changes should happen to Compilation.assets after sealing the 
Compilation.
    Do changes to assets earlier, e. g. in Compilation.hooks.processAssets.
    Make sure to select an appropriate stage from Compilation.PROCESS_ASSETS_STAGE_*.
(Use `node --trace-deprecation ...` to show where the warning was created)
asset main.bundle.js 32.6 KiB [emitted] (name: main) 1 related asset
asset package.json 632 bytes [emitted] [from: package.json] [copied]
cacheable modules 26.2 KiB
  modules by path ./node_modules/electron-squirrel-startup/ 18.7 KiB
    modules by path ./node_modules/electron-squirrel-startup/node_modules/debug/src/*.js 15 
KiB 4 modules
    ./node_modules/electron-squirrel-startup/index.js 1 KiB [built] [code generated]
    ./node_modules/electron-squirrel-startup/node_modules/ms/index.js 2.7 KiB [built] [code 
generated]
  ./src/main/main.ts 6.82 KiB [built] [code generated]
  ./node_modules/file-url/index.js 684 bytes [built] [code generated]
external "path" 42 bytes [built] [code generated]
external "url" 42 bytes [built] [code generated]
external "electron" 42 bytes [built] [code generated]
external "child_process" 42 bytes [built] [code generated]
external "tty" 42 bytes [built] [code generated]
external "util" 42 bytes [built] [code generated]
external "fs" 42 bytes [built] [code generated]
external "net" 42 bytes [built] [code generated]
webpack 5.21.2 compiled successfully in 4313 ms

asset renderer.bundle.js 1000 KiB [emitted] (name: main) 1 related asset
asset index.html 196 bytes [emitted]
runtime modules 937 bytes 4 modules
modules by path ./node_modules/ 990 KiB
  modules by path ./node_modules/scheduler/ 31.8 KiB 4 modules
  modules by path ./node_modules/react/ 70.6 KiB 2 modules
  modules by path ./node_modules/react-dom/ 875 KiB 2 modules
  modules by path ./node_modules/css-loader/dist/runtime/*.js 3.78 KiB 2 modules
  ./node_modules/style-loader/dist/runtime/injectStylesIntoStyleTag.js 6.67 KiB [built] 
[code generated]
  ./node_modules/object-assign/index.js 2.06 KiB [built] [code generated]
modules by path ./src/ 5 KiB
  modules by path ./src/app/styles/*.less 3.16 KiB
    ./src/app/styles/index.less 385 bytes [built] [code generated]
    ./node_modules/css-loader/dist/cjs.js!./node_modules/less-loader/dist/cjs.js!./src/app
/styles/index.less 2.78 KiB [built] [code generated]
  ./src/renderer/renderer.tsx 373 bytes [built] [code generated]
  ./src/app/components/App.tsx 1.48 KiB [built] [code generated]
webpack 5.21.2 compiled successfully in 4039 ms

But I get Cannot read property 'send' of undefined

enter image description here

If I set in App.tsx :

const sendProxy = window.api.send;

I get the same error and the window is not rendered :

enter image description here

What am I doing wrongly with Typescript and with Electron IPC? Looking forward to your kind help

Solution

  • Below is my setup based on https://www.electronforge.io, which also adds typings for the exposed api. Hope it helps, even if not a focused answer.

    In package.json (using @electron-forge package.json setup, webpack + typescript template), under entryPoints, make sure you have:

    "preload": {
    "js": "./src/preload.ts"
}

    In src/index.ts where you create your BrowserWindow, use the magic webpack constant to reference the bundled preload script (maybe your preload script didn't get bundled?):

    const mainWindow = new BrowserWindow({
    webPreferences: {
      preload: MAIN_WINDOW_PRELOAD_WEBPACK_ENTRY
    }
  });

    Contents of src/preload.ts:

    import { contextBridge } from "electron";
import api from './api'

contextBridge.exposeInMainWorld("api", api);

    src/api/index.ts just exports all features of the api. Example:

    import * as myFeature from "./my-feature";

// api exports functions that make up the frontend api, ie that in
// turn either do IPC calls to main for db communication or use
// allowed nodejs features like file i/o.
// Example `my-feature.ts`: 
// export const fetchX = async (): Promise<X> => { ... }

export default {
    ...myFeature
}

    Typescript 2.9+ can recognise your api functions like api.fetchX by adding a global declaration, e.g. src/index.d.ts (reference):

    declare const api: typeof import("./api").default;

    ...which you need to reference from tsconfig.json:

    { 
  ...
  "files": [
    "src/index.d.ts"
  ]
}

    All that done and you should be good to call api.fetchX with typing support (ymmv by IDE) from renderer-side without importing anything. Example App.tsx:

    import * as React from 'react'
// do not import api here, it should be globally available

export const App = () => {
  useEffect(() => {
    (async () => {
      const x = await api.fetchX();
      ...
    })();
  }, []);

  return <h1>My App</h1>
}