Looking ahead at commands such as `t` and `f` that will also need to accept a single character, I think we could save some lines by making this a bit more generic. Could we get away with making this a `SingleCharInputViewModel` with a constructor something like

```coffeescript
class SingleCharInputViewModel
  constructor: (@operator, @class, @completeCommand) ->
    ...
```
that replaces the existing `replace` specific things with those variables?