New GuldenDex app

New GuldenDex app

Interview with Harm Jan van Kammen

The Gulden community knows you as the owner of Taxi Noord. Today you are releasing the GuldenDex app. Are you a developer?

Back in 2009 when I got my hands on a HTC Dream (T-Mobile G1 in Europe) and soon after that my first iPhone, I knew that mobile apps were the future. I dreamt of building apps that would change the world and being the best app developer there is. Sadly, it didn’t go as planned.

Back then, I was creating websites using HTML and PHP for some years already. My projects varied between applications that supported our company with administrative tasks and managing my own Online Text-based Mafia RPG game called GangsterGlobe.EU. I still have that domain after all these years, hard to let go of it when I remember all the fun times i had!

Did you make any mobile apps before?

Over the years I did try to make mobile apps, yes. But I just couldn’t understand how it worked or bring myself to learning Object-C for iOS and Java for Android. Xcode and Android Studio looked like pure magic to me! 

In 2015 I needed an Android app for my taxi dispatch system so we could use simple and cheap Android tablets in our taxi’s to send fare’s to our drivers. A colleague of mine pointed me to the site (It’s gone now) and because my lack of skills to create apps I posted my project on the website to have it created by someone else. It took 2 coders and 2 weeks for me to realize that this wasn’t the way to go. If I wanted to make this work I had to do it myself.

Ok, so what did you do?

I went home early on a Friday and turned off my phone. My refrigerator was packed with Red Bull and a cupboard full with snacks. I downloaded Android Studio and I was ready to begin! It took 3 entire days without much sleep but the “app” was done. After the excitement of creating my first app went away I couldn’t see it as an app like I always wanted to build. It was a glorified web browser with some location services. It was a means to an end and nothing more. We still use it to this day and last year I published it to the Google Play store so that it could be easily updated over all our devices. I also gave creating an Android Widget a shot. It worked out quite well and I got 1.000+ installations!

Nice! But that was years ago. Tell us about the GuldenDex app. Why did you pick up building apps again?

About 2 months ago somebody told me about React Native and I was amazed with all the possibilities it offers. Although I’m late to the party, I finally had the chance to create apps! I took an Udemy course given by Stephen Grider in what I think was a record time and started my journey into creating apps.

I decided to start off with an app for my favorite cryptocurrency Gulden. If you don’t know Gulden I encourage you to check out their website and join their Slack community at

GuldenDex is my first real app!

So what is GuldenDex? is a simple app, for now, where you can check the actual trade data available from Nocks Trade. You can fill in your portfolio to see what it’s currently worth and the actual price movement over the last hour. The last price and the graph are the main attraction for now. But I have plenty of ideas for the future. As this is my first app I’ll probably never stop working on it. 

For future releases I already have the following ideas on my list:

  • More insight into your portfolio.
  • Push notifications that you can set yourself based on the last price.
  • Nightmode
  • Further Nocks API integration for keeping up to date with your trade orders and get insights about your trading.

Did you had any help from Nocks?

Yes. To get the data I needed for my app i used the extremely well documented Nocks API. I use the trade-market call to get all the data I use on my app. Together with my own PHP wrapper class called nocksPHP that is available on GitHub. Check out the Nocks API documentation here. To get acces to their api you’ll need an account at

I definitely learned a lot in the past 2 months and i’m still learning new things about React Native everyday! I really love the platform and i’m excited about creating more apps with it. I had to overcome many challenges to build this app since it’s my first one. But React Native has a great community where people can help you with the problems you encounter!

Oh, that was very technical, thanks. Love to give it a try. Were can we download the app?

It’s available for iOS and Android!

Thanks Harm Jan for your story. Are you going to make more apps?

Yes, definitely, so let’s get to it!

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