iPhone app: integrating a Mag Strip Reader

I know someone who publishes an iPhone app which currently has an input field for the credit card number. But, this means the user must type it in, which is error prone and slow. So, I hope to reconfigure without even any coding changes to the app.

This is the kind of device I need to use...

http://magstripe.org/imag.html

https://www.amazon.com/ID-Technologies-ID-80110010-001-Shuttle-MagStripe/dp/B01CLJV0YW/ref=pd_day0_328_4?_encoding=UTF8&psc=1&refRID=1R9YXSDV7B64JVP5WD78

https://www.amazon.com/ID-Tech-Idmr-Al30133-Reader-iPhone/dp/B00VGX2QV6/ref=sr_1_2/146-2848884-2147402?ie=UTF8&qid=1511036967&sr=8-2&keywords=iphone+card+swipe

https://www.amazon.com/Deftun-Bluetooth-Wireless-Magstripe-Collector/dp/B01N11U9IJ/ref=pd_sbs_328_5?_encoding=UTF8&psc=1&refRID=94J69FY5A1Q7NJ4B5877

My question is...

Can one of these be used along with the app, on an iPhone, to get that credit card number into that field, but do so without  requiring any modifications to the app?

I see that some require a merchant account, and those will not work. The app I am describing must run and communicate with the server. It can not use an existing app to transmit the information.

All I need is a way to automate the manual key entry of the credit card #. So, can any of these readers be configured to insert the credit card # into that field?

I suppose, worst case, if the card reader inserted the CC# into a note, so it could be copied and pasted, that might be better.

Thanks