Note: Checkout part one about web frameworks options in Crystal.

Once your Kemal app grows a little bit it seems obnoxious to declare tons of variables that are automatically passed down to the view.

Personally what I like to do when I’m feeling that the amount of variables is too damn high and the logic used inside the Kemal router is getting hard to reuse - is to introduce a presenter (simple class, no magic there) that basically wraps whole logic responsible for initializing variables I will need. And usually I drop-in some convenient helper methods.

To decouple it even further and make it a little bit more flexible I tend to implement decorators. If you use ecr there is handy def_to_s class method that allows you to specify template file to use when to_s is called on your object. And it seems to me that it’s a perfect combination. The use case is as follows:

<!-- somewhere in static view we can just call -->
<%- @movies.each_with_index do |movie, idx| -%>
  <%= Decorators::Movie.new(@presenter.category, movie, idx + 1) %>
<% end %>
# src/decorators/movie.cr
module Decorators
  class Movie
    @percentage : Int32

    def initialize(@category : String, @movie : Mappings::Movie, @number : Int32)
      # here I calculate @percentage that I will later use as width of a progress bar
    end

    # inside that partial you will have access to all instance variables
    ECR.def_to_s "src/views/movies/_movie.ecr"
  end
end

I think it’s a neat and convenient approach for building small static sites with Kemal.