I am looking for something like in this simplified example: with\ %{key: true} <- result = a_function_returning_map() do :success else _ -> IO.inspect(result) end The with construct seems like a good fit for the stream of various actions that may fail and return different results. I can recogni…

Good and Bad Elixir might give you some ideas.

Well, I read it (thank you) and basically it says “Back to deeply nested cases/ifs and Co.”, although not because there’s no way to pass result value(s) down to else. Rather because the author believes it to be at all “bad” to match specific errors in the else block

You’re throwing away the parameter passed to the else block. It will receive the result of the expression that failed. iex(2)> with %{key: true} <- Map.new() do ...(2)> :success ...(2)> else ...(2)> result -> IO.inspect(result, label: "fail") ...(2)> end fail: %{}

[image] gregvaughn: You’re throwing away the parameter passed to the else block That’s because I simplified the example down to the very core :slight_smile: Normally I’d match things there. The question was about passing additional information/variable, which (leaving aside whether this is “…

It can be done with wrapping tuples, but it’s ugly. You have to do things like: with {:ok, result} <- get_result(), {{:ok, other_result}, result} <- {{get_other_result()}, result} do :success else {_, result} -> IO.inspect(result) end If you find yourself in that situation, then it’s prob…

[image] silverdr: Well, I read it (thank you) and basically it says “Back to deeply nested cases/ifs and Co.” Not quite. What about the suggestion to introduce a unified error struct? We went with that approach and it works pretty nicely. The error struct doesn’t have to be global to the whol…

[image] gregvaughn: It can be done with wrapping tuples I see.Thank you. Didn’t think of that. Maybe because [image] gregvaughn: it’s ugly indeed :slight_smile: [image] gregvaughn: If you find yourself in that situation, then it’s probably worth stepping back to look at the bigge…

[image] silverdr: when I am confronted with a well confined piece of not-really-reusable business logic I rather take a dozen lines of the author’s perfectly readable “Bad Elixir” than the larger, more complex and less readable “Good Elixir” :wink: I think the else was added to the language at s…

[image] stefanchrobot: The else clause was there from the beginnings of with. Looking through Elixir’s codebase, I haven’t really found instances of using more than one patterns in else. Correct. I generally find having more than one clause in else an anti-pattern. We either use it as a “catc…

[image] stefanchrobot: The else clause was there from the beginnings of with This source says: " As of Elixir 1.3, with/1 statements support else", which I interpret that it was added in 1.3. Correct me if I am wrong or the source is wrong. [image] josevalim: I generally find having more…

`with` construct usage question - variables in `else`

Questions & Help Questions

stefanchrobot November 12, 2021, 10:29am 12

You’re right. with was introduced in 1.2 and else got there in 1.3.