HTML input attributes helper

Installation

gem "input_attributes_from_validators"

The main idea

HTML inputs have powerful controls over browser via attributes:

• validations (min, max, minlength, maxlength, required) and
• keyboards variations (inputmode, step).

Normally you write those HTML attributes manually or forget about them, but most of them can be inferred from model validations and the DB column name.

How to use

Provided that you have validators on your model:

class Review < ActiveRecord::Base

  validates :comment, presence: true, length: { min: 3, max: 1_000 }
  validates :score, numericality: { only_integer: true, in: 1..5 }
end

Individual helper methods

This gem exposes a set of helper methods, one for the corresponding HTML attribute:

validated_inputmode @rating, :comment #=> "text"
validated_minlength @review, :comment #=> 3
validated_maxlength @review, :comment #=> 1_000
validated_required  @review, :comment #=> true

validated_inputmode @rating, :score   #=> "numeric"
validated_min       @rating, :score   #=> 1
validated_max       @rating, :score   #=> 5
validated_step      @rating, :score   #=> 1

Aggregate method

There is also a method that returns a hash with all the values:

resolved_input_attributes(record, attribute_name) #=>
{
  inputmode:  <String || NilClass>,,
  max:       <Integer || NilClass>,
  maxlength: <Integer || NilClass>,
  min:       <Integer || NilClass>,
  minlength: <Integer || NilClass>,
  required: <Boolean>,
  step:      <Integer || Decimal>,
}

so you don’t have to repeadedly pass the record and the attribute name:

= form_for model: @review do |f|
  - attrs = resolved_input_attributes(@review, :score)

  = f.number_field :size \
                    inputmode: attrs[:inputmode], \
                    max:       attrs[:max], \
                    min:       attrs[:min], \
                    required:  attrs[:required], \
                    step:      attrs[:step]

  = f.text_field :description \
                    inputmode: attrs[:inputmode], \
                    maxlength: attrs[:maxlength], \
                    minlength: attrs[:minlength], \
                    required:  attrs[:required]

Less useful methods

Search for validators with certain conditions:

validators_for(record: @review, attr: :comment, type: :length, options: [:maximm])
#=> 255

validators_for(record: @review, attr: :score, type: :numericality, options: [:less_than, :less_than_or_equal_to])
#=> 5

Also

validated_value(record: @review, attr: :comment, type: :length, options: [:maximm])
#=> 255

validator_type_to_class :presence     #=> ActiveRecord::Validations::PresenceValidator
validator_type_to_class :numericality #=> ActiveRecord::Validations::NumericalityValidator

Todo

• [ ] pattern attribute