‘Iacta alea est’

Basic Form: Field Decoration

Yesterday we created a Field class that contained all of the source data necessary for building out a field in HTML.

Today we can look at how to decorate this data with some helper methods to calculate the necessary derivatives.

Our categorised and sorted list of data defines the following derived elements coexisting alongside the original data:

• input[id] and label[for]
• input[name]
• help[id] and input[aria-describedby]

Let’s add some methods to our field class:

class Field
  …
  def input_id
    [object_name, name].join("_")
  end
  
  def input_name
    "#{object_name}[#{name}]"
  end
  
  def help_id
    [input_id, "help"].join("_")
  end
end

This is all we need. We could memoize the input_id to ensure it isn’t being calculated from scratch each time. This way we ensure that it remains identical (an edge-case but it feels safer given the values need to be identical for the label and input to correspond properly in the HTML).

class Field
  …
  def input_id
    @input_id ||= [object_name, name].join("_")
  end
  …
end

I believe this is everything we would need for our basic field before rendering it to HTML.

—Saturday 3rd July 2021.