Assuming you prefer Apple's keyboards, I'm pretty sure the Magic Keyboard with Bluetooth works with iPads. The downside is you'd have to manage charging the keyboard and the iPad, but on the bright side you could choose to get the keyboard with the numeric keypad.

I have heard really good things about the keyboards for the iPads. I’m still using an iPad Air 2 with a Logitech Bluetooth keyboard which works wonders.

There are code editing apps for iOS, but I don’t know what they're capable of these days. Some use cloud servers, but as soon as you know you want the option then the laptop is probably the way to go. Happy hunting!

grab ipad with bluetooth mechanical keyboard