2017-11-05 11:33 GMT+01:00 Nicolas Cellier <
[email protected]>:
>
> Ah, I messed up, UndefinedSorter must not be chained, it must be a
> wrapper!
> Otherwise comparing to nil will resort to sorting by properties and fail...
>
> SortFunction>>undefinedFirst
> ^UndefinedSorter descending wrap: self
>
> UndefinedSorter>> collate: value1 with: value2
> "sort all nil according to the direction (first if -1, last if +1),
> then"
> value1 ifNil: [value2 ifNil: [^0] ifNotNil: [^direction]].
> value2 ifNil: [^direction negated].
> ^sorterForNonNil collate: value1 with: value2
>
> It's important to have the UndefinedSorter :
> - decoupled from property sort, because it can be generally usefull
> - collating 2 nil as 0, so that another property can be chained
>
I like your idea.
It also forced me to think that direction itself should be implemented as
wrapper. I would name it InvertedSortFunction:
InvertedSortFunction>>collate: value1 with: value2
^(actualSortFunction collate: value1 with: value2) * -1
If we will do it then direction will be not part of SortFunction. And all
current functions will be in fact ascending.
And to explicitly reflect this fact I would introduce AscendingSortFunction
as their superclass.
InvertedSortFunction and ChainedSortFunction will stay subclasses of
SortFunction.
So what you think?
>
> In
>
> people sortBy: #name ascending undefinedFirst , #age descending
>
> we could then have people with name nil still sorted by age, what is not
> possible with current implementation
>
>
