I read an article on the Dockyard blog and I’m wondering why they used an equal sign with a with statement. [image] Authorization Considerations For Phoenix Contexts - DockYard Should authorization be handled in the Web layer or within the context? Let's find out which approach is bette…

with is a macro that evaluates a set of expressions and the <- symbol is a hint to that macro that the right-hand side will either match the left, bind any unbound variables, and then continue to the next expression, or it won’t match, and it will follow the else clause matching if present, or just …

I think it should be: with {:ok, page} <- CMS.get_page(id), :ok <- Authorizer.authorize(:update, page, current_user), {:ok, page} <- CMS.update_page(page, page_params) do ... or page = CMS.get_page!(id) with :ok <- Authorizer.authorize(:update, page, current_user), {:ok, page} <-…

In this case, with being the only block in the function it does not matter, but still its a good thing to keep the scope of a variable as small as possible.

[image] felix-starman: {:ok, page} = CMS.get_page(id) In this case error’s message will change also (pattern match error). This way phoenix cannot handle this error as “not found” (404) in production if debug_errors: false, it will be 500 error.

[image] focused: I think it should be: with {:ok, page} <- CMS.get_page(id), Generally my expectation when I see get_… is that it will return the thing or nil or a provided default value. If you want to return {:ok, thing} or an error fetch_… would be a more consistent naming. In regards t…

[image] bennelsonweiss: In regards to the original question, I use = in with clauses to indicate that I’m not matching on that result. Sometimes you may need to do something between matches in a with that you don’t need to match on (like creating a changeset) and = signals intent better Sorry…

I keep re-reading your answer and it’s not sticking. By raising (assuming that ! does as intended) the error will fall through the with clause, and does not appear to be handled. I’m going to assume that’s a mistype :thinking: What would be the difference if we use page <- CMS.get_page!/1? It woul…

[image] woohaaha: and does not appear to be handled. I’m going to assume that’s a mistype It’s probably not a mistype at all. You don’t need to handle everything in a with, and in their case they’re not handling anything in with. Since they’re not handling anything in a with everything is fa…

Thank you! I think I got the intent :clap: Your example is more clear to me than the blog post. Things that got me confused: Errors falling through with. Then why use with? The first condition in the with is page = CMS.get_page!(id), but if we don’t care about matching, why even put it in the wit…

@bennelsonweiss explained it perfectly. They use with because they want to handle those errors by matching on them in action_fallback like: def call(conn, {:error, %Ecto.Changeset{} = changeset}) do conn |> put_status(:unprocessable_entity) |> put_view(MyAppWeb.ChangesetView) |> r…

Why was equal sign used in with statement?

Questions & Help Questions

woohaaha July 14, 2021, 4:20am 7

Sorry for asking, would you mind showing me an example?