Ring IOS Software Developer interview questions

I had a very brief discussion by phone and then they demanded that I write an entire iOS app for them, unpaid, in Swift, before I could be granted an onsite interview. I don't normally work for free so I declined. In the Los Angeles area, many startups are demanding free coding before any real interview, which is borderline illegal and certainly disrespectful of them, especially because often the app they request is something that can be put into production for it has monetary value.