A resume is only used for the screening process. Once I've decided this person might have what it takes, I invite them in for an interview, and the resume isn't

A resume is only used for the screening process. Once I've decided this person might have what it takes, I invite them in for an interview, and the resume isn't looked at again. The interview process equally checks technical viability and culture fit, and the interviewee will not be hired if they don't pass both with flying colors. To answer your questions: The characteristics I look for depend on the culture I'm building within the team. The core concepts are more or less "Do you know how to solve this problem?" not necessarily "Here, solve this problem in this interview, without any of the resources you would normally have." A portfolio isn't required, but gives us another window into your technical ability. A GitHub profile chalk full of open source contributions, or a StackOverflow profile with high reputation showing very high communication skills are always a plus. I don't have any experience hiring iOS developers or Ruby developers, so I'll abstain from answering that question. Hope this helps!