How to write a custom model in elixir / phoenix without being object-oriented?

Question

I am building a little test app with the Phoenix Framework. I cannot use Ecto since my DB is not supported. But I still want the MVC pattern. So I need a way to implement custom models. Since I'm coming from RoR I always catch myself thinking in Object Oriented Programming patterns where you have a class definition and instances with attributes that you can get and set. So that something like this is possible:

@mike = User.new
@mike.name = "Mike Power"
@mike.save

# ect

But this is clearly not how Elixir works.

I'm having a hard time wrapping my head around how to approach this. The implementation should allow me to:

Have attributes
Store values
Manipulate values
Validate values
Save them to my database

The best way I have come up with so far is using structs. So something like this:

defmodule User do
  defstruct name: "", age: 0

  def sayhello do
    IO.puts "Hi, I am #{name}"
    # This is not working, I just put it here to make a point
  end
end 

tim = %User{}
# -> %User{age: 0, name: ""}
tim = %User{name: "Tim Turbo", age: 25}
# -> %User{age: 25, name: "Tim Turbo"}
tim.name
# -> "Tim Turbo"

# We can also change the values 
tim = %User{name: "Michael"}
# -> %User{age: 25, name: "Michael"}

# It also makes sure that only the values defined in the struct can be set (which is nice)

tom = %User{unknown: "something"}
# ** (CompileError) iex:11: unknown key :unknown for struct User

Using vex I would even be able to implement validations quite easily

defmodule User do
  defstruct username: nil, password: nil, password_confirmation: nil
  use Vex.Struct

  validates :username, presence: true,
                       length: [min: 4],
                       format: ~r/^[[:alpha:]][[:alnum:]]+$/
  validates :password, length: [min: 4],
                       confirmation: true
end

So I am basically asking:

Is this the way to go? Or is there a better one?
And would I implement the function to actually save the user to the database also in my User module? Where I just enter the parameters

Something like this:

user = %User{params}
User.create user

reading ecto's source is a good starting point: github.com/elixir-lang/ecto — sobolevn

Alex Troush Alex Troush · Accepted Answer · 2015-11-12T17:44:00

My thoughts on reverting OO paternilized way of thinking:

Try to build your logic around data and what you need to do with data. Not the object's you need to create and modify.

On example of "Say Hello":

defmodule UserWelcomer do
  def sayhello(user) do
    IO.puts "Hi, I am #{user.name}"
  end
end

Basicly you trying to be functional all the way and working with "User" data through different functions.

Sorry, this not an answer. Just a comment that off the comment limits.

How to write a custom model in elixir / phoenix without being object-oriented?

2 Answers