OCaml: Type Checking Objects

object ocaml instanceof typechecking
Nick Heiner picture Nick Heiner · Sep 15, 2009 · Viewed 17.5k times · Source

If I have an object, how can I determine its type? (Is there an OCaml equivalent to Java's instanceof operator?)

Answer

newacct picture newacct · Sep 15, 2009

OCaml has structural typing for objects rather than nominative typing as in Java. So the type of an object is basically determined (and only determined) by its methods. Objects in OCaml can be created directly, without going through something like a class.

You can write functions which require that its argument objects have certain methods (and that those methods have certain types); for example, the following method takes an argument that is any object with a method "bar":

let foo x = x#bar

Related questions

Checking if a key exists in a JavaScript object?

How do I check if a particular key exists in a JavaScript object or array? If a key doesn't exist, and I try to access it, will it return false? Or throw an error?

Read More
What is the most efficient way to deep clone an object in JavaScript?

What is the most efficient way to clone a JavaScript object? I've seen obj = eval(uneval(o)); being used, but that's non-standard and only supported by Firefox. I've done things like obj = JSON.parse(JSON.stringify(o)); but question the …

Read More
Converting an object to a string

How can I convert a JavaScript object into a string? Example: var o = {a:1, b:2} console.log(o) console.log('Item: ' + o) Output: Object { a=1, b=2} // very nice readable output :) Item: [object Object] // no idea what's inside :(

Read More