I have the following use case:
I want to develop a desktop application, which will run on a Raspberry Pi. I decided to use Electron to build the desktop application and Angular as the frontend framework (1).
I need to use some npm modules for my application in order to communicate with the GPIO-pins or over ethernet tcp communication ('net' node module). I tried to import these in my Angular application (for example import {Socket} from 'net';), but I don't get them working.
I get the following error when trying to construct the net socket like this:
let client = new Socket();
Uncaught (in promise): TypeError: undefined is not a constructor (evaluating 'new net.Socket()')
Is this an error in the base architecture, that I can't run code, which depends on the backend, in the angular frontend. Or am I doing something else wrong?
I also found capacitor (2), which allows to call native sdks. I tried to implement my own plugin, but I get the same error as above.
Thanks for your help.
(1) https://angularfirebase.com/lessons/desktop-apps-with-electron-and-angular/
(2) https://capacitor.ionicframework.com/docs/plugins/
It seems like you have a little confusion about Electron, even thou it is not the classical client:server model, ...
Lets understand Electron first:
Main and Renderer Processes
The main process is for handling/creating BrowserWindows(Renderer) And
for some communication from one renderer-Window to an other one.
(maybe some other special stuff too)
The renderer is where you really run the most of your app. With node,
you have all you need there.
you then notice you will be needing a channel between the renderer process (web page) and the main process.
Don't worry, here is where remote comes in handy :
Use main process modules from the renderer process.
The remote module provides a simple way to do inter-process communication (IPC) between the renderer process (web page) and the main process.
...even the other way round...
Note: For the reverse (access the renderer process from the main
process), you can use webContents.executeJavascript.
So at the end you will be able of using all the magick in both sides.
Related
We have an install of Node.js running on a Windows Server 2012R2 web server. A developer created an application for us using Next/React/Node (I'm not a web developer so I'm unsure of the specifics of the various development tools used). This app works fine when manually started on the command line like this:
C:\NodeApps\pacifield>"C:\PROGRAM FILES\NODEJS\NODE.EXE" C:\NodeApps\pacifield\node_modules\next\dist\bin\next start
However this requires someone to manually login and restart the app whenever the server is rebooted or the app stops for whatever reason. I am trying to setup PM2 to run the app. I have it up and running fine until you browse to the app - at which point you get the following error:
next-server.ts:306 Error: Invalid hook call. Hooks can only be called inside of the body of a function component. This could happen for one of the following reasons:
1. You might have mismatching versions of React and the renderer (such as React DOM)
2. You might be breaking the Rules of Hooks
3. You might have more than one copy of React in the same app
See https://reactjs.org/link/invalid-hook-call for tips about how to debug and fix this problem.
at resolveDispatcher (c:\NodeApps\pacifield\node_modules\react\cjs\react.development.js:1476:13)
at useContext (c:\NodeApps\pacifield\node_modules\react\cjs\react.development.js:1484:20)
at useSession (c:\NodeApps\pacifield\node_modules\next-auth\dist\client\index.js:75:39)
at Provider (c:\NodeApps\pacifield\node_modules\next-auth\dist\client\index.js:588:12)
at processChild (C:\NodeApps\pacifield\node_modules\react-dom\cjs\react-dom-server.node.development.js:3353:14)
at resolve (C:\NodeApps\pacifield\node_modules\react-dom\cjs\react-dom-server.node.development.js:3270:5)
at ReactDOMServerRenderer.render (C:\NodeApps\pacifield\node_modules\react-dom\cjs\react-dom-server.node.development.js:3753:22)
at ReactDOMServerRenderer.read (C:\NodeApps\pacifield\node_modules\react-dom\cjs\react-dom-server.node.development.js:3690:29)
at Object.renderToString (C:\NodeApps\pacifield\node_modules\react-dom\cjs\react-dom-server.node.development.js:4298:27)
at Object.renderPage (C:\NodeApps\pacifield\node_modules\next\dist\server\render.js:596:45)
I have checked and there is only the one installation of React in C:\NodeApps\pacifield\node_modules\react and the other suggestions don't seem to make sense when it runs fine outside of PM2. I have checked with ProcessExplorer that all the environment variables are the same (except for the additional ones PM2 adds) when the app is run from the command line vs. PM2.
Anyone have any suggestions?
Hooks can only be call inside of functional component or inside another hook.
take note: Invalid Hook Call Warning
Notify your frontend developer it.
I'm currently building a react native app which uses async storage. I've got conditionals within the components to decide whether to make requests to the API or use the data stored in memory. So to test out these conditionals I regularly have to clear the AsyncStorage using AsyncStorage.clear().
This works if I have it in one of the components, however it would be more practical to have it in a seperate script - which brings me to my question:
I want to have a script as below:
import AsyncStorage from '#react-native-community/async-storage';
AsyncStorage.clear();
console.log('STORAGE CLEARED');
and then run it using a command like node clearStorage.js (and later an npm script).
However I'm getting an error saying 'Cannot use import statement outside a module'.
Am I missing anything glaringly obvious/trying to do something I shouldn't? I've tried changing the file type to .mjs with no luck.
If you need to do this, you can't use a nodejs script because the node script will never get to the native side, because async-storage is a native library and it connects directly to Android or IOS.
Another solution may be at the start of the application, you can run that code, or create a Button just for dev mode and when click clean the data.
and the error 'Cannot use import statement outside a module'. it's because nodeJs don't understand the syntax import AsyncStorage from '#react-native-community/async-storage'; they need a transpiler like babel.
A Brief Backstory
I have been implementing several upgrades to an Angular 8 application such as server-side rendering, and Google Analytics. As most developers do, I would code then test then move on to the next task. Typically I use ng serve to run the application as I am developing.
With Server-side rendering, to test speed, lazy-loaded images, etc, you need to use a node express server running on a generated JS file. After building, etc, I use Node prerender (my js file is prerender.js) to see what the application will look like prerendering on the server.
When I run this command, I should not get any errors, and I know my prender file will start a local server on port 4000.
The Problem
I get errors when running a node express server that I do not get when running with ng serve I recently got an error that said:
Unhandled Promise rejection: Cannot read property 'subscribe' of undefined ; Zone: <root> ; Task: Promise.then ; Value: TypeError: Cannot read property 'subscribe' of undefined
at new ApplicationRef (C:\4towerdevelopment\dist-stage\server\main.js:45910:37)
at _createClass (C:\4towerdevelopment\dist-stage\server\main.js:37184:20)
at _createProviderInstance (C:\4towerdevelopment\dist-stage\server\main.js:37138:26)
at initNgModule (C:\4towerdevelopment\dist-stage\server\main.js:37044:32)
at new NgModuleRef_ (C:\4towerdevelopment\dist-stage\server\main.js:38176:9)
at Object.createNgModuleRef (C:\4towerdevelopment\dist-stage\server\main.js:38159:12)
at NgModuleFactory_.create (C:\4towerdevelopment\dist-stage\server\main.js:50821:25)
at C:\4towerdevelopment\dist-stage\prerender.js:29175:43
at ZoneDelegate.invoke (C:\4towerdevelopment\dist-stage\prerender.js:481:26)
at Object.onInvoke (C:\4towerdevelopment\dist-stage\prerender.js:28683:33) TypeError: Cannot read property 'subscribe' of undefined
at new ApplicationRef (C:\4towerdevelopment\dist-stage\server\main.js:45910:37)
at _createClass (C:\4towerdevelopment\dist-stage\server\main.js:37184:20)
at _createProviderInstance (C:\4towerdevelopment\dist-stage\server\main.js:37138:26)
at initNgModule (C:\4towerdevelopment\dist-stage\server\main.js:37044:32)
at new NgModuleRef_ (C:\4towerdevelopment\dist-stage\server\main.js:38176:9)
at Object.createNgModuleRef (C:\4towerdevelopment\dist-stage\server\main.js:38159:12)
at NgModuleFactory_.create (C:\4towerdevelopment\dist-stage\server\main.js:50821:25)
at C:\4towerdevelopment\dist-stage\prerender.js:29175:43
at ZoneDelegate.invoke (C:\4towerdevelopment\dist-stage\prerender.js:481:26)
at Object.onInvoke (C:\4towerdevelopment\dist-stage\prerender.js:28683:33)
The closest this gets me to figuring what actually is causing the problem is letting me know that a provider somewhere is causing this error. Looks like something should be an observable rather than a subscription. Beyond that, I guess I just start looking through my providers. My question is:
How can I force Angular to possibly throw this error when developing using ng serve?
If I can't, is there a better way to debug this current error besides combing through each provider? Or at least a way to tell what service is causing the issue?
Thank you.
UPDATE: Basic repo with problem here. I made a new angular project, made sure dependencies were up to date, installed ngUniversal per this post, and received this same Unhandled promise message when running node prerender
Verbatim I went to to the Angular cli website, made a new project (default Angular version installed was 8.3), installed Angular Universal, and tried to build. Same error message as above.
This looks like it was ApplicationRef that triggered the error, and that class is provided internally by the Angular core.
It could be failing in the constructor of the class, and there are a few calls to subscribe on Zone observables. I don't think you're going to find anything in your source code that directly relates to this error. It looks like a build configuration problem.
https://github.com/angular/angular/blob/bb52fb798c8578c461d21aee2b7623232184a5d3/packages/core/src/application_ref.ts#L562
I do not know what could possibly produce this problem, but I would start a new project with SSR and compare the differences to your current project.
Eventually, I dropped the angular 6 approach using pre-render, and went with the latest universal package. There seems to be no problem building using npm run build:ssr and serving dist/server.js in an express server. I am not sure what the problem was with the pre-render approach, but it seems to be outdated anyways. #Reactgular thanks for the feedback.
I'm wondering if it's possible to use command line arguments with ReactJS (not react-native). For example, is it possible to input a simple string and have it be saved as a variable so it can be displayed? The npm yargs module is the kind of thing I'm looking for, but I couldn't get that to work because the child process it spawns apparently doesn't work in a browser.
Edit: I've also tried something like including {process.argv[0]} in say an h1 tag, but nothing shows up.
React doesn't have anything special for command line arguments. In fact, it is primarily designed as a DOM library. You could use yargs and then pass the values to a React component.
For example you run this command in terminal or cmd
npm start -- foo
foo is your argument.
You can print your like this
// print process.argv
process.argv.forEach(function (val, index, array) {
console.log(index + ': ' + val);
});
in your script.
React runs is client-side
React is a client-side library. It runs in a web page, on a browser. The end-user doesn't use the command-line to "run" React, therefore command-line arguments are not available to the end-user.
For developers
As a developer, you do use tools to start a development server and launch a browser that is running React. Most likely, you're using Create React App. You can use environment variables to pass variables/arguments to React. Specifically, the documentation offers these examples:
# on Linux and macOS
REACT_APP_NOT_SECRET_CODE=abcdef npm start
# on Windows (cmd.exe)
set "REACT_APP_NOT_SECRET_CODE=abcdef" && npm start
Note that these variables are embedded into React at build time, when Create React App bundles and builds your app (kind of like compiling). This means that if you build your React project and then transfer the output files to another server and try to pass new variables, nothing will change.
For servers
If your React build files are on a server and you want to be able to pass command-line arguments to the server and have React change, this is also possible, but largely depends on what software you are using to serve. Broadly, the server would take the runtime argument and pass it into the template which renders your React app. Then any Javascript that runs on that page can access the arguments.
In my nwjs application i am using React to build my UI. Currently, React is being loaded via a <script> tag in the main file, index.html. index.html has another <script> tag which loads main.js containing code which defines and renders my React components as well as requiring (require()) a few Node modules such as "fs" and "McFly".
This all seems to be working, however when i try using another node module (react-inlinesvg) i get an error, "document is undefined".
Having looked online for help, i have come to the conclusion that React now believes that it is being run on the server? Which is odd, as before i started using the react-inlinesvg module it was happily rendering components using React.render (clientside rendering).
If you need any more context or information then please ask.
It could be that you are rendering on the server side, or also that you are rendering both sides. In the second case you could simple nest the line that is causing you error with:
if (process.env.BROWSER) {
the line causing the error
}
If the error disappears, it means that you are on the server side also!
I hope this helps...
Basically if you code is universal (or isomorphic, if you want...) with this check you can execute the code only on client side, you want to do this to use a particular style-sheet for example:
if (process.env.BROWSER) {
require("../style/main.scss");
}
Naturally if you want to do stuff server-side you can check
if (!process.env.BROWSER) {
}
if any one face this he can solve it in 2 ways:
Solution 1: if you are using nw.js 15 or above try to enable mix context mode:
in your package.json add this flag:
"chromium-args": "--mixed-context"
Solution 2: expose document to the global object using this hack:
global.document = window.document;