Extracting common module concerns

[adamnoto]

I am new to both Crystal and Marten, but so far they look great! I wonder tho, how do we extract common behavior to a module the way rails do with "concerns."

For my case, I tried to define SlugGenerator which then can be included to all models having slug field. The module is as follow.

module SlugGenerator
  after_initialize :generate_slug, on: :create

  private def generate_slug
    self.slug = Nanoid.generate(
      size: 21,
      alphabet: "1234567890abcdefhjkmnprtxy",
      secure: true
    )
  end
end

However, including them will raise an error: Error: undefined method 'after_initialize' for SlugGenerator:Module. Please advise.

[ellmetha]

Hey! 👋

You will probably want the after_initialize call to run in the class in which your SlugGenerator module is included. To ensure that this is the case, the simplest solution is to use the #included macro (see the macro hooks documentation).

For example:

module SlugGenerator
  macro included
    after_initialize :generate_slug, on: :create
  end

  private def generate_slug
    self.slug = Nanoid.generate(
      size: 21,
      alphabet: "1234567890abcdefhjkmnprtxy",
      secure: true
    )
  end
end

Let me know if it works!

[adamnoto]

Awesome, it works! I love it so much, I am interested to help contribute in a year-ish I hope, currently I am familiarizing with this and the language. Great work!