Develop Reference

Can I write a React Native app without a Mac?

I'm choosing a cross platform framework to create an app, React Native would be my first choice because I'm already proeficent with React and it will allow full code sharing with my Deno based back-end but here a problem arises, I don't have a Mac and it seems that the oly way to develop React Native apps without a Mac is by using Expo, sadly it can't be an option for me since I need have very strict privacy requirements to follow and by these the telemetry which Expo apps sends to Expo team is not acceptable.
Considering that my app would use very few device native features (just CRUD operations on application local storage and QR code reading) which are already covered by cross platform modules it would be possible to write my app on a Windows laptop, debug it on an Android device, build it using a free CI/CD platform which includes Linux and Mac agents to get working Android and iOS packages with can be distributed to the respective stores?

As you can see in React Native documentation, you can write code for both platforms on Windows machine, but for building an publishing IOS application, you must use Mac machine
A Mac is required in order to build your app for iOS devices. Alternatively, you can refer to our environment setup guide to learn how to build your app using Expo CLI, which will allow you to run your app using the Expo client app.
Read doocs here: Running On Device

I made an android app using flutter, is there a way to build an IPA from the same code?

So I built an android app using flutter on Android studio but I see that in order to build an IPA I need to use Xcode on a MAC device so I was really wondering what to do to transfer the flutter app to Xcode? or do I need to rewrite the whole code again?
I tried using a ci/cd service too it would build the app in .app format but would never install on my IOS device, I followed another procedure to transfer .app to .ipa but still it can't be installed so I'd be really grateful if someone could give me an insight on what to do at least
thanks in advance

Flutter can directly compile an iOS and Android version. You do not need to rewrite anything(unless you have Android native code in your App). Just open your Project on a Mac with Flutter and Xcode installed and compile it by running flutter build ios.
You won't be able to do anything without a Mac though. Since Xcode is required to sign your App and Apple doesn't let you do that on any other OS.

I developed an android application with cordova and I want to convert it to iOS as well

I developed an android application with cordova and I want to convert it to iOS as well. Before starting my project I heard that we are able to convert same project with multiple platforms using cordova. But now I don't know how to convert my project to IOS. Can any one suggest good tutorial OR examples to do it.
And also mention what are all prerequisites to convert my android application to IOS using phone gap.
Suggest me some tutorials with examples.

First, you'll need an actual Mac computer. I suggest a MacBook Air, as they are cheaper than an iPhone. Then purchase an Apple developer license (USD 100/year) if you plan to submit this app to the App Store. Finally, you can migrate your Cordova source code to Xcode to compile the iOS version as explained in this guide:
Build Cordova iOS app from Visual Studio for Windows
The artice explains how to create a new app in Xcode and then export your source code from the Windows PC to the Mac. You can safely ignore all references to Visual Studio if you aren't using it, because it's not needed: Just follow the steps from the For your iOS app section.

How to build my react native app with TeamCity?

I start using Team City and my app builds with react native version 0.60.5...
I was wondering what will be the best and the easier way to build my app for iOS and android.
For iOS I was thinking using the Xcode plug.
For android I'm thinking to use Docker but its complicated and taking time to develop..
Does someone has any recommendation what to use for building my android app or Docker is a good solution?
And about the iOS, are you recommend use the Xcode plug or any other idea?
Thank you for the help

You can easily use TeamCity to automatize your build for Android, check the official documentation for more information:
You just need to be careful specifying the requirements for build your project for React Native, like:
version of react native, version of expo-cli, version of node that you are using in your project and etc...
For IOS, i recommend using fastlane, check this official tutorial from Apple.
Don't forget that you need to have an developer account for build to ios in React-Native.

how to build an iphone apps in phonegap online or on windows? (without mac system)

I developed android apps in phonegap and it is successfully work on all android versions now I want to run my app on iPhone which is ceated in phonegap. I know xcode IDE but its a need Mac System. I don't have mac system. I have some questions...
Q.1) can I develop and create iphone apps on a cloud for phonegap(free and license)?
Q.2) can I create ipa online?
Q.3) can we run Mac in VM, but I dont want to use that(its slow,sluggish and painful to use).
Thanks in advance.

If you want to develop for cross platform that is, Android and iOS, you can try Mobione Studio, which doesn't require Mac, it runs only on Windows.
It's a paid IDE and design studio, which has 15 days trial period.
Also, it's project structure is same as that of Phonegap, as it has Cordova base.

Q1) Yes you can.
Q2) Yes, with Phonegap BUild you get an ipa.
Q3) I don't know about this.
Be aware - like the previous reply said - you'll need to use a service to upload to iTunes if you don't have a Mac.
If you have a Mac (of any kind) you can use that to upload the ipa you build with Phonegap Build.