Virtus pg array type for Sequel

gistfile1.rb

module Virtus
  class PGArray < Attribute
    primitive Sequel::Postgres::PGArray

    def primitive
      options[:primitive]
    end

    def coerce(value)
      Sequel.pg_array(value)
    rescue
      value
    end

    def value_coerced?(value)
      value.instance_of?(Sequel::Postgres::PGArray)
    end
  end
end

class Params
  include Virtus.model(strict: true)
  
  attribute :arr, Virtus::PGArray
end

gistfile2.txt

irb(main):007:0> Virtus::Attribute.build(Virtus::PGArray, strict: true).coerce([1,2,3])
=> [1, 2, 3]
irb(main):008:0> Virtus::Attribute.build(Virtus::PGArray, strict: true).coerce('')
Virtus::CoercionError: Failed to coerce "" into Sequel::Postgres::PGArray

tl;dr: You may not need to call primitive method within the custom attribute class body, unless you want to make Virtus use the custom attribute #coerce method to define all attributes of the given primitive.

---

I just found out that unless you want to write a generic coercer for any value of class Foo, you better omit the primitive Foo part.

For example, I wrote a custom coercer for BigDecimal, let's call it BigDecimalWithOneDecimalPoint. It tried to coerce the given value to a BigDecimal and then round it to one decimal point.

However, because I used primitive BigDecimal within the BigDecimalWithOneDecimalPoint definition, Virtus was using it for all BigDecimal values. Even if I specified that BigDecimal is the type of an attribute:

attribute :foo, BigDecimal

…Virtus would still use BigDecimalWithOneDecimalPoint for the coercion.

Removing the primitive call seems to solve the problem. However, in order to make the strict mode error message correct, you can no longer use options[:primitive] in the primitive method. For now, I just made mine method return the desired primitive.

I made a reproduction of the issue. However, I'm not sure if I should submit it as a separate Virtus issue, because I think calling primitive or defining value_coerced? is using the private API of Virtus. And yeah, I remember you're not working on Virtus. 😉

So I post it here to make people aware of the caveats of calling primitive.