value.from( object, keyPath )

In the example below, a keyObservable is created that is one-way bound to the value at outer.inner.key. When outer.inner.key changes, keyObservable.value is updated, but changes to keyObservable.value do not update outer.inner.key.

import DefineMap from "can-define/map/map";
import value from "can-value";

const outer = new DefineMap({
  inner: {
    key: "hello"
  }
});

const keyObservable = value.from(outer, "inner.key");
// keyObservable.value === "hello"

keyObservable.value = "aloha";
// Error thrown because the value isn’t settable