Decisions according to environment

Question

I am trying to convince others that the following first code snippet is bad practice and the second snippet is best practice.

Bad practice:

// There is only one implementation of Adapter
public function setAdapter(Adapter $adapter)
{
    $this->adapter = $adapter;
}
public function persist(Entity $entity): void
{
    if ($this->env->dryMode === true) {
        return;
    }
    $this->adapter->persist($entity);
}

Best practice:

// Can inject different adapters, also something like a `DryModeDbAdapter`,
// that simply does nothing when `persist` is called.
public function setAdapter(AdapterInterface $adapter)
{
    $this->adapter = $adapter;
}
public function persist(Entity $entity): void
{
    $this->adapter->persist($entity);
}

I need references that back my thesis. Do you know any? Is there a specific keyword that refers to this programming situation? Like "implementation configuration agnostic" or something.

Answer 1

It looks like the refactoring you are proposing to change from what you say is bad practice to what you say is good is what Fowler calls replace conditional with polymorphism.

Whether or not its an improvement is context dependent, but that should be enough to help you find more discussion.

Answer 2

A key question here is when dryMode is known. If it's only known after the adapter is constructed the polymorphic solution wont work.

The polymorphic solution allows you to add more cases later without changing existing, tested, deployed code. You have to ask yourself if those cases are likely to be needed. Booleans have few values so don't really indicate many cases have been anticipated.

The polymorphic solution isn't free. It takes more code, more time to create, more time to read and understand. Yes there's amazing flexibility here. But it comes at a cost. Be sure it's worth it.

---

There are many boolean toggles "liveMode", "dryMode", "devOnly", - Daniel W.

That is not encouraging.

A polymorphic solution works best when one property can take on many states. Not when many properties are on or off independently. I mean, you can make it work but, yuck.