Recommended way to check for Properties

Lets say I have this Model for Picture component:

let Model = Cycle.createModel(Props => ({
  src$: Props.get("src$").startWith("#"),
  title$: Props.get("title$").startWith(""),
  favorite$: Props.get("favorite$").startWith(false),
}));

In React we have propTypes to declare required properties and their expected types. What do you think is the best direction to implement that in Cycle?

[ivan-kleshnin]

@tel thank you very much for such detailed explanation.

I’ve tried Flow a few times. I found it less mature, but I’d be tempted to use it exactly and only for its treatment of nulls. They are such a terrible thing to have in a language.

As I remember from theory it’s not a null on itself being terrible but default “nullability” of all types in JS / Java. Anyway, it’s an interesting point in Flow.

I think ultimately Flow wants to be a type-checking layer atop JavaScript while TypeScript wants to be a new language which just so happens to superset JavaScript. I feel the latter is a better place to stand.

New language makes a difference, yes. There are pros and cons. I would rather go with ClojureScript, I’m really tired of JS, but there are a lot more libraries, much more job opportunities in JS. And some super-valueable tools like Webpack are unique to JS ecosystem. ClojureScripts guys seem to stuck with React so who is really on the cutting edge? – that’s an open question.

[tel]

default “nullability” of all types in JS / Java

Yeah, that’s one way to see it. The technical form I like the most is the notion that all types are “pointed” in that they all contain a special value “null”. It turns out that it’s rare to have semantics amenable to this treatment (but consider mathematical groups which have “null” but handle it gracefully).