Fl4m3Ph03n1x

Fl4m3Ph03n1x

Is there a way to have Elixir Records without default values?

Background

I am trying to find a cheap and easy way to create New Types in Elixir, and Records seem to be just what I would need.

Problem

However, Elixir records require one to define default values. Not only that, it also allows one to create empty records (which would then be populated with said default values).

For my specific use case, this is a problem. Not only don’t I have anything that can be used as a default value, I also don’t want to allow the users of my code to create empty records.

Now, I understand this is likely a well intended choice, most likely so it can interface nicely with Erlang records, but it causes an usability issue on my end: it allows the creation of non valid data.

Questions

I understand there is probably no solution for this conundrum using Records only, so I was wondering if there are alternatives in the wild of libraries or even hacks to accomplish this.

I personally have found nothing, right now I have the feeling my only solution is to write my own macro.

  • Is there a way to have Records not accept default values?
  • If not, what community libraries are out there that could help fulfill the role of creating a New Type?

Marked As Solved

Fl4m3Ph03n1x

Fl4m3Ph03n1x

Answer

  1. Is there a way to have Records not accept default values?

No. This is not possible with Records. Records were never intended for this use case and forcing this abstraction into them would only complicate things. While one could use a wrapper new method, it would still be a lot of boilerplate and all the validation for type would be on the user.

  1. At the time of this writing, there are none. However, in another post I created a macro that achieves this purpose: How to define Macro for a new Type? - #10 by Fl4m3Ph03n1x - Questions / Help - Elixir Programming Language Forum

In that post I propose an API and then I refine it with the community’s help. For those of you who are curious, it can be used like this:

type.ex

defmodule Type do
  import NewType

  deftype(Name, String.t())
end

test.ex

defmodule Test do
  alias Type.Name

  @spec print(Name.t()) :: binary
  def print(name), do: Name.extract(name)

  def run_1 do
    # dialyzer complains !
    Name.new(1)
  end

  def run_2 do
    # dialyzer complains !
    print("john")
  end

  @spec run_3 :: binary
  def run_3 do
    print(Name.new("dow"))
  end
end

Also Liked

OvermindDL1

OvermindDL1

If you want to validate data then make a constructor function for it, I generally call it new.

Where Next?

Popular Backend topics Top

chasekaylee
Hi there everyone! Recently, I have fallen in love with programming with Elixir and have been having so much fun with it. I have been do...
New
s2k
I have this code in a file that’s used to … render templates. require 'erb' require 'ostruct' MISSING_CONFIG_MARKER = :config_key_and_v...
New
sampu
I have a use case where a client is invoking a Rest endpoint via a load balancer, which in turn invokes a third party endpoint which is r...
New
JimmyCarterSon
Hello, I am working on a new application with Elixir, Dish_out. I want to see Data I follow this tutorial with Elixir Casts. However, I ...
New
Fl4m3Ph03n1x
Background PS: the following situation describes an hypothetical scenario, where I own a company that sells things to customers. I have ...
New
Manish_bose
Can anyone help me how to convert a long data to wide data in SQL without using hard coding? Regards Manish
New
Fl4m3Ph03n1x
Background I am moving towards defined data structures in my application, and I find that TypedStruct is quite useful. Questions Howeve...
New
sona11
I studied very basic PHP (I believe). After that, I feel like I’ve gotten a handle on the language. My dream is to work as a web develope...
New
Fl4m3Ph03n1x
Background I have a release file inside a tarball. However I want the final release to have some additional files and to move things aro...
New
jaeyson
Hi! I have clarifications (please correct me, as I mostly mix/confuse this details) with the following: The term RAG here where it read...
New

Other popular topics Top

ohm
Which, if any, games do you play? On what platform? I just bought (and completed) Minecraft Dungeons for my Nintendo Switch. Other than ...
New
AstonJ
Curious to know which languages and frameworks you’re all thinking about learning next :upside_down_face: Perhaps if there’s enough peop...
New
New
AstonJ
You might be thinking we should just ask who’s not using VSCode :joy: however there are some new additions in the space that might give V...
New
AstonJ
I’ve been hearing quite a lot of comments relating to the sound of a keyboard, with one of the most desirable of these called ‘thock’, he...
New
AstonJ
In case anyone else is wondering why Ruby 3 doesn’t show when you do asdf list-all ruby :man_facepalming: do this first: asdf plugin-upd...
New
PragmaticBookshelf
Author Spotlight Jamis Buck @jamis This month, we have the pleasure of spotlighting author Jamis Buck, who has written Mazes for Prog...
New
AstonJ
If you want a quick and easy way to block any website on your Mac using Little Snitch simply… File > New Rule: And select Deny, O...
New
Margaret
Ask Me Anything with Mark Volkmann @mvolkmann On February 24 and 25, we are giving you a chance to ask questions of PragProg author M...
New
PragmaticBookshelf
Fight complexity and reclaim the original spirit of agility by learning to simplify how you develop software. The result: a more humane a...
New