kostonstyle
I wrote a a function that delete the content of database.
Consider following code snipped:
defmodule Seeds do
def delete_db(values) when is_list(values) do
cond do
length(values) > 0 ->
Repo.delete_all(values)
true ->
{:ok}
end
end
end
When I call the delete_db function, it will happen a side effect, the data on db will be deleted.
My question is, do I follow functional specification?
Thanks
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First Post!
gon782
What exactly does that mean? It’s not technically a function, no, because it has a side-effect. The reality of Erlang & Elixir is that there can be side-effects in procedures anywhere. Pure functions in these languages are an ideal; something to strive for, not law.
It’s also not law in Haskell, for example, but is clearly marked as happening, at least. I would suggest not fretting about using side-effects in Elixir. Instead, pay attention to where you can do without them by passing data. Don’t do this to blindly follow ideals, but to get code that can be used in any context and with predictable results.
Most Liked
gon782
Well, with refactoring in mind it might be better to simply do this:
It’s short, splits the procedure up into cases neatly and asserts structure at the same time.
josevalim
Here is my take:
gon782
The possible issue is that you’re not necessarily asserting that it should be a list if you ended up using only
values, yeah. I prefer code to be as assertive as possible about structure and constants if possible. If something in the function itself makes the assumption that lists are passed in, we should try to make things that don’t follow that crash horribly, IMO.On a related note: I vastly prefer the structural form to is_list().
Last Post!
peerreynders
This topic made me realize that I need to work more on retraining my mind to see multiple function clauses not as overloaded functions but as distinct parts of one single function.
Edit: Sorry meant to be a general remark, not a specific reply.