Once a contract is created on the Ethereum blockchain it cannot be modified. Said another way - it’s written in stone. Updating your code is problematic … actually impossible Updating a smart contact can be a problem if you need to change the code …
Donn Felker is the founder of Caster.IO. He's is a best selling author in mobile development and he also co-hosts the Fragmented Podcast - a Podcast for Android Developers. Most recently he's been diving deep into blockchain with a focus on Ethereum and Solidity. Follow him on Twitter, Instagram or visit his site.