Odtnhj

I'm using dry-types and dry-struct and I would like to have a conditional validation.

for the class:

class Tax < Dry::Struct
 attribute :tax_type, Types::String.constrained(min_size: 2, max_size: 3, included_in: %w[IVA IS NS])
 attribute :tax_country_region, Types::String.constrained(max_size: 5)
 attribute :tax_code, Types::String.constrained(max_size: 10)
 attribute :description, Types::String.constrained(max_size: 255)
 attribute :tax_percentage, Types::Integer
 attribute :tax_ammount, Types::Integer.optional
end

I want to validate tax_ammount as an Integer and mandatory if `tax_type == 'IS'.

dry-struct is really for basic type assertion and coercion.

If you want more complex validation then you probably want to implement dry-validation as well (as recommended by dry-rb)

See Validating data with dry-struct which states

Please don’t. Structs are meant to work with valid input, it cannot generate error messages good enough for displaying them for a user etc. Use dry-validation for validating incoming data and then pass its output to structs.

The conditional validation using dry-validation would be something like

TaxValidation = Dry::Validation.Schema do

 # Could be:
 # required(:tax_type).filled(:str?, 
 # size?: 2..3, 
 # included_in?: %w(IVA IS NS)) 
 # but since we are validating against a list of Strings I figured the rest was implied
 required(:tax_type).filled(included_in?: %w(IVA IS NS)) 
 optional(:tax_amount).maybe(:int?)

 # rule name is of your choosing and will be used 
 # as the errors key (i just chose `tax_amount` for consistency)
 rule(tax_amount:[:tax_type, :tax_amount]) do |tax_type, tax_amount|
 tax_type.eql?('IS').then(tax_amount.filled?) 
 end
end

• This requires tax_type to be in the %w(IVA IS NS) list;


• Allows tax_amount to be optional but if it is filled in it must be an Integer (int?) and;


• If tax_type == 'IS' (eql?('IS')) then tax_amount must be filled in (which means it must be an Integer based on the rule above).

Obviously you can validate your other inputs as well but I left these out for the sake of brevity.

Examples:

TaxValidation.().success?
#=> false
TaxValidation.().errors
# => :tax_type=>["is missing"]
TaxValidation.(tax_type: 'NO').errors
#=> :tax_type=>["must be one of: IVA, IS, NS"]
TaxValidation.(tax_type: 'NS').errors
#=> 
TaxValidation.(tax_type: 'IS').errors
#=> :tax_amount=>["must be filled"]
TaxValidation.(tax_type: 'IS',tax_amount:'NO').errors
#=> :tax_amount=>["must be an integer"]
TaxValidation.(tax_type: 'NS',tax_amount:12).errors 
#=> 
TaxValidation.(tax_type: 'NS',tax_amount:12).success?
#=> true