CE/unit toggle 

This method name doesn't suggest what it really does. And I think it pulls in the wrong parameter, and internally derives values that should be parameters.

Thinking very broadly, the action that should be presented to the VC is logically closer to

```objc
-setToggleUnits:(Unit)
```
 It could delegate its strings independently `-stringForUnit:(Unit)`, which can handle the pluralization. That way the interfaces between concerns aren't strictly tied to the presence of a "/".