# Weekly Iteration - Primitive Obsession

## What is it?

## What does it look like in Ruby?

Over relying on hashes/arrays

```ruby
[5, 30]
```

```ruby
1930
```

```ruby
{ name: "Joël", age: 42 }
```

## Why is it a bad idea?

* Harder to read
* Many domain concepts combined together
* In Ruby, need to define methods somewhere
* Allows representing invalid values
* Hard to change

## What are the solutions?

More objects

```ruby
class Money
  def from_cents(cents)
    new(cents / 100, cents % 100)
  end

  def initialize(dollars, cents)
    @dollars = dollars
    @cents = cents
  end
end
```

## What about functional languages like Elixir?

We don't have objects so what's the alternative?

## Discuss custom types in Haskell/Elm

Compilers reward you for avoiding primitives

```elm
type Seach =
  { query : Maybe String
  , results : Maybe (List String)
  }
```

```elm
type Search
  = NotStarted
  | TermSelected String
  | ResultsFetched String (List String)
```

## General ideas

Try to program at a higher level of abstraction with domain concepts rather than
language primitives.