It’s absolutely necessary to…
Have a command of Swift and Xcode
For starters, it is enough to know the current Swift and how to work with Xcode.
Manage version control
Commit, push & pull in Git are as automatic for you as brushing your teeth.
We have our own coding style and we would prefer to see spaghetti on a plate.
Know how to work with API
You are able to parser JSON from REST API into a database (using documentation).