Why is the molecule's value constructor called every time useMolecule is evaluated?

[mfurtak]

Hi folks,

I'm just getting started with Bunshi, and I'm a little confused by the behavior I'm seeing.

If I create a molecule with no molecule or scope dependencies:

const expensiveObjMol = molecule(() => {
  // expensive object creation
  // ...
  return expensiveObj
})

And then I use that with:

export const MyComponent = () => {
  const expensiveObj = useMolecule(expensiveObjMol);

  return (
   // ...
  );
};

My observation is that the molecule value constructor function is called every time the useMolecule is evaluated. This means that the work of creating a new expensive object is done every time MyComponent is rendered, even though only the first value created is ever returned by useMolecule. So, if that's accurate, Bunshi is honoring the contract that I'll always get the same object reference, but it seems like it is also doing work that isn't desirable/useful.

My expectation would be that a dependency injection framework would avoid doing the work of creating new objects when they wouldn't be used.

Is my expectation wrong for Bunshi? Do I have the facts about the behavior right? What am I missing?

Thanks,
-Mike

[loganvolkers]

Hi @mfurtak I believe that this was reported as a bug in #39 and has been resolved in Bunshi 2.1.0

There are also new lifecycle hooks (onMount and onUnmount) to do more fine-grained control of memory-related operations.