It’s absolutely necessary to…
Have a command of Swift and Xcode
You know when to use which paradigm, feel at home in Xcode, and understand the code in Objective-C (and ideally, you are able to write it in a sensible way).
Manage version control
You can use Git-flow, understand the sense of code review, and can boast to us about a project that more people have worked on together.
You understand the significance of maintaining a unified code style and you write your code like poetry (which, as opposed to contemporary works, is a pleasure to read).
Know how to work with API
Parsing JSON from REST API into a database is the minimum. Not being afraid of Websockets and Firebase is a sound basis. If you are able to design your own API, we are head over heels in love.
Have been through some team work
And have the results to show for it, which we can download from the App Store and test out on our own iPhones. When you show us your GitHub, we will not torment you with a practical task.
MVC, MVVM, and so on. You know what their meanings are, when to use them – and you have practical experience with them.
We appreciate when someone is not too shy to ask and can also ask for a second opinion, but… from a senior, we would expect that he/she will more often give advice rather than ask for it.