As I said, it's a property list, so the only validation I get is that it is a well-formed property list. It's the validating the values that I'm stuck on. Is there something better than code like this? NSObject *name = dict[@"name"]; if (![name isKindOfClass:[NSString class]]) { // report failure } In Swift I would be using the as? operator, and I guess that this is the closest equivalent. (My memory only recalled the isa method, but further searching turned up isKindOfClass.)

Nice to know that I'm not alone. SwiftUI does make sense for the subviews, so I'll probably try to make the main view with AppKit. It will be an interesting challenge.