normalizes str to decimal in rails 7.1

Question

Is is possible to use the new normalizes in Rails 7.1 to convert types before it is assigned. For example,

create_table "procedures" do |t|
  . . . 
  t.float "duration"
  . . . 
end

class Procedure < ActiveRecord
  normalizes :duration, with: -> (d) {
    match = /^(?:(\d+)h)\s?(?:(\d+)m$/.match(d.to_s)
    if match
      match[1].to_i * 60.0 + match[2].to_i
    else
      d.to_f
    end
  }

  expect(Procedure.new(duration: "3h 30m").duration).to eq(210.0) # Fail: duration == 3

I'm either confused about the intended use of normalizes or, I'm using it correctly but I have a bug somewhere.

Answer 1

Other than normalization, there are a few ways you can do it:

Simply override duration= method, if you only need to convert it one way:

class Procedure < ApplicationRecord
  def duration=(value)
    self[:duration] = if /^(?:(\d+)h)\s?(?:(\d+)m)$/ =~ value.to_s
                        $1.to_i * 60 + $2.to_i
                      else
                        value
                      end
  end
end       

or make a custom attribute type:

# config/initializers/types.rb

class DurationType < ActiveRecord::Type::Float
  def cast(value)
    if /^(?:(\d+)h)\s?(?:(\d+)m)$/ =~ value.to_s
      value = $1.to_i * 60 + $2.to_i
    end
    super
  end
end

ActiveRecord::Type.register(:duration, DurationType)

class Procedure < ApplicationRecord
  attribute :duration, :duration
end

---

You could serialize if you want to save a float into the database but show a string representation:

class Procedure < ApplicationRecord
  class Duration
    def self.load(value)
      return unless value
      "%dh %dm" % value.divmod(60)
    end

    def self.dump(value)
      if /^(?:(\d+)h)\s?(?:(\d+)m)$/ =~ value.to_s
        $1.to_i * 60.0 + $2.to_i
      else
        value
      end
    end
  end

  serialize :duration, coder: Duration
end

>> Procedure.create!(duration: "3h15m")
  TRANSACTION (0.1ms)  begin transaction
  Procedure Create (0.6ms)  INSERT INTO "procedures" ("duration") VALUES (?) RETURNING "id"  [["duration", 195.0]]
  # -> ----------------------------------------------------------------------------------------------------^^^^^
  TRANSACTION (0.1ms)  commit transaction
=> #<Procedure:0x00007fb6c009bfb8 id: 1, duration: "3h 15m">