module_function

### What it does?
* `module_function` allows exposing instance’s methods so they can be called as they would be class methods.

```ruby
module User
  def name
    'Hello Sam'
  end
end
```

If you try to do this:

```ruby
user = User.new
user.name
```

You're gonna receive an error because `modules` do not respond to the `new` method.

### How can we use it?

You can use this useful method `module_function`:

```ruby
module User
  module_function
  
  def name
    'Hello Sam'
  end
end
```

And call the `name` method like  `User.name`

1. Use `module_function` to use all the methods inside a module as class methods or
2. Use `module_function :name` to only apply it in a specific method

### A second option to do it

Another option to do so is using `extend self` instead:

```ruby
module User
  extend self
  
  def name
    'Hello Sam'
  end
end
```

samantha-bello
September 29, 2021