DEV Community: Sushant Bajracharya

Mix task to search for alias name

Sushant Bajracharya — Sun, 08 May 2022 11:09:53 +0000

I recently had to work on a project which used multi alias

alias ModA.{ModB, ModC}

Searcing is difficult on project like this so I wrote a mix task that would look for the alias name and then print the file and line number on the terminal.

https://github.com/sushant12/find_alias

Building a game server in elixir

Sushant Bajracharya — Wed, 05 May 2021 08:18:31 +0000

I am not an expert so take this post with a grain of salt like every other posts of mine.

https://github.com/sushant12/snake_ladder/tree/v0.2.0

Okay, now that it is out of the way let me tell u what I think a game server is first. I think that a game server is a process that keeps the state of the game and their implementation depends on the type game itself.

As a kid, I used to play snake and ladders a lot. So, I built one but with minimal rules and two players only.I am not going to go through the code one by one , what I would like to tell you is what approach I took to build it.

Since I am building a 2P game, I have to keep track of who is what. So, whoever visits the root url is "Player 1" because a random token and a foreman=true is appended to the url. Player 2 will have just the random token in their url.

When someone visits the root url, I am treating it as start of a new tournament which will start a new "GameServer" which is a GenServer process. The "GameServer" is a child of DynamicSupervisor which was started with "mix phx.server". The state is kept in sync between the connected players via phoenix pubsub.

I know that the game will need to have structures so that's why the "game" and "player" struct. The "game" struct would store the list of players, dice state, game token and current players turn. The "player" struct stores the player name and their position. The "game" struct has functions to help manipulate/update itself. For eg: updating the dice state when user rolls a dice.

I have used liveview to dynamically show the changes in the UI. I do need to show some animations like rolling a dice when clicked on "roll", moving the piece, etc for which I will use js hooks.

So, that's about it for now. I have couple more things that I want to implement like cleaning off zombie game servers, notifying user when a player leaves the game, etc. I guess when I finish implementing it, it will be a time for new blog.

live_render from phoenix controller

Sushant Bajracharya — Wed, 21 Apr 2021 13:54:44 +0000

Recently, I rendered a liveview from one of my controller and I had to pass some params to that liveview. You can pass the params if you put it in the session option but that didnt felt right to me.

So, I figured I ask the community and I got to know when not to use live_render in the controller instead and got a reply from the creator himself.

when you have an existing controller and dead views already in place and you want to add in a bit of live stuff

assign in redirect

Sushant Bajracharya — Sat, 17 Apr 2021 07:28:07 +0000

So, I just found out that if you are redirecting to other routes, the assign that you did in your conn wont be available to the next template.

That's because assign stores value in current request's connection struct and if we use

conn
|> assign(:something, "sdf")
|> redirect(to: route)

it will never make it to another template.

alias in elixir

Sushant Bajracharya — Thu, 08 Apr 2021 09:19:07 +0000

This post will not explain about alias , rather I would like to share a piece of code that caught me off guard.

alias Rumbl.Accounts # context
alias Accounts.User # schema

def first_name(%User{name: name}), do: name

If I compile it, it would give me compilation error Rumbl.Accounts.User__struct__/0 is undefined.

It's pretty obvious why, looking at the code now. Since the Rumbl.Accounts is already aliased, the Accounts.User assumed Accounts to be Rumbl.Accounts.

Just updating their position would fix it

Understanding "warning: redefining module x" in elixir

Sushant Bajracharya — Sun, 21 Mar 2021 05:49:38 +0000

Take this article with a grain of salt.

This particular warning is telling you that even after loading the module, elixir is trying to recompile it.

There are different ways to clear such warning in the internet like removing the _build directory. It did not work for me initially.

In my case, I had an unused variable in my eex file. Since my project was configured to treat warnings as error in my credo setting, it failed to compile leaving me with a lot of "redifing module" warnings. And in that noise, another warning was hidden which pointed out on prefixing the unused variable.

After prefixing the unused variable and mix do clean, phx.server, those warnings went away

A free pomodoro app

Sushant Bajracharya — Sun, 23 Aug 2020 07:02:35 +0000

Visit https://pomo-do.netlify.app/ for a demo

I have to learn alpinejs for work and I was looking for a pomodoro app where I can check my history for FREE.

So, I wrote a pomodoro app with alpinejs. It's like killing two bird with one stone.

TBH the pomodoro app could have been written on vanilla js but like I said I just wanted to learn it.

Make it work, make it right, make it fast

The code is filled with a lot of conditions which I MIGHT improve later on.

Emulate bash "history" but for iex

Sushant Bajracharya — Sun, 16 Aug 2020 07:06:24 +0000

Personally, I think the bash command, history, is a neat productivity tool. I use it all the time history | grep and I wanted the same thing in IEx as well.

To search through the history in IEx, you need to first enable it. Then either use up arrow keys or ctrl + r to search. That's cool but still not exactly what I need.

So, the first thing I had to do was to find the place where the history is stored.

# run it in your IEx
:filename.basedir(:user_cache, "erlang-history")

The history files are written by erlang's disk_log, so there will be weird characters when you open it in your editor. My initial thought was, if the history is written by disk_log:log/2 which uses erlang:term_to_binary/1, then I can read those history files with erlang:binary_to_term/1. But it turns out when writing history, disk_log appends some kind of weird binaries which you can find in disk_log.hrl eg <<12,33,44,55>>. So, I tried disk_log:chunk/2 to parse it.

# this will print the content of the history file with header
# in IEx, it will print charlists
# in erl, it will print strings

:disk_log.chunk(:'$#group_history', :start)

It did parse the history but it had weird headers and also didn't give me the whole content of all the history files.

{{:continuation, #PID<0.81.0>, {1, 52393}, []},
 [
   {:vsn, {0, 1, 0}},

I found a file called group_history.erl. It has two public api load/0 and 'add/2'. The load/0 api parsed and returned the whole history just as I wished.

:group_history.load()

And then I finally wrote the rest of the code to emulate bash history command

defmodule History do
  def search(term) do
    load_history()
    |> Stream.filter(&String.match?(&1, ~r/#{term}/))
    |> Enum.reverse()
    |> Stream.with_index(1)
    |> Enum.each(fn {value, index} ->
      IO.write("#{index}  ")
      IO.write(String.replace(value, term, "#{IO.ANSI.red()}#{term}#{IO.ANSI.default_color()}"))
    end)
  end

  def search do
    load_history()
    |> Enum.reverse()
    |> Stream.with_index(1)
    |> Enum.each(fn {value, index} ->
      IO.write("#{index}  #{value}")
    end)
  end

  defp load_history, do: :group_history.load() |> Stream.map(&List.to_string/1)
end

I have put this code in my .iex.exs file so that I can call it whenever I am in my IEx.

History.search("map")
History.search()

Hi there!!

Hi, I am looking for awesome opportunities to work with Elixir. If you are hiring or need a hand to finish your pet/side project then let's get connected. Here is my email sussyoung9[at]gmail[dot]com

Generate n digit random number in elixir

Sushant Bajracharya — Fri, 24 Jul 2020 06:11:42 +0000

To generate n digit of random number you can do

Enum.random(10,20)

It will generate 2 digit number between 10 and 20

postgres timestamp and timestamp(0)

Sushant Bajracharya — Fri, 24 Jul 2020 05:19:49 +0000

timestamp(p) where p can be a value from 0 - 6.

p stands for precision which retains the number of fractional digits in the seconds field.

Ecto's Repo.insert

Sushant Bajracharya — Wed, 22 Jul 2020 05:23:43 +0000

If you have default values set in your database, then Repo.insert will not return its value.

To return the value, you have to pass Repo.insert(returning: true)

If you dont want to do returning: true you can set default return value in your schema.

schema "rooms" do
  field :enable_chat, :boolean, default: false
end

Then when you do insert, it will return the default false

TIL: Import app.css in app.js

Sushant Bajracharya — Sat, 30 May 2020 11:05:51 +0000

impoet app.css in app.js for webpack to compile it