basic string converter macro for crystal

example.cr

require "json"
require "yaml"

require "./string_converter"

data = {test: "1", value: "3.5"}
json_data = data.to_json
yaml_data = data.to_yaml

class Data
  JSON.mapping({
      test: {type: Int16?, converter: StringConverter::Int16},
      value: {type: Float64?, converter: StringConverter::Float64},
  })

  YAML.mapping({
      test: {type: Int16?, converter: StringConverter::Int16},
      value: {type: Float64?, converter: StringConverter::Float64},
  })
end

puts Data.from_json(json_data).inspect #=> #<Data:0x84a3e70 @test=1, @value=3.5>
puts Data.from_yaml(yaml_data).inspect #=> #<Data:0x84a3e70 @test=1, @value=3.5>

string_converter.cr

module StringConverter
  {% for typ in [Int16, Int32, Int64, Float32, Float64] %}
    class {{typ}}
      def self.from_json(parser) : ::{{typ}} | Nil
        str = parser.read_string
        
        ::{{typ}}.new str
      rescue ArgumentError
        nil
      end
      
      def self.from_yaml(parser) : ::{{typ}} | Nil
        str = parser.read_raw
        
        ::{{typ}}.new str
      rescue ArgumentError
        nil
      end
    end
  {% end %}
end