Ndto - An Erlang library for Data Transfer Objects validation

What is ndto?

ndto is an Erlang library for generating DTO (Data Transfer Object) validation modules from schemas.


Validating incoming data is a critical step to ensure the integrity, consistency, and security of your application’s data flow. However, writing custom validation logic for each DTO can quickly become a time-consuming and error-prone task.

With ndto, you can define validation schemas that describe the structure and constraints of your data. These schemas are then used to automatically generate validation modules, reducing development time and avoiding human-induced errors in the validation step.

A basic example

  1. Define an ndto schema.
Schema = #{
    <<"type">> => <<"string">>,
    <<"minLength">> => 8,
    <<"pattern">> => <<"^hello">>
  1. Generate a module using the ndto:generate/2 function.
DTO = ndto:generate(string_schema, Schema).
  1. Load the generated module on the fly.
ok = ndto:load(DTO).
  1. Call the is_valid/1 function from the generated module to validate your data.
true = string_schema:is_valid(<<"hello world">>).
false = string_schema:is_valid(<<"hello">>).
false = string_schema:is_valid(<<"hi world">>).

ndto schema language

ndto defines a custom data type (i.e., ndto:schema()) to represent schemas.

%%% ndto.erl
-type schema() ::
    | universal_schema()
    | ref_schema()
    | enum_schema()
    | boolean_schema()
    | integer_schema()
    | number_schema()
    | string_schema()
    | array_schema()
    | object_schema()
    | union_schema()
    | intersection_schema()
    | complement_schema()
    | symmetric_difference_schema().

The goal is to provide an abstraction that decouples the library functionality from a specific schema specification format. This enables developers to use ndto to generate modules for schemas defined in the specification language that better fits their development environment by implementing an ndto_parser.


While ndto provides an interface for the generation and loading of validation modules in runtime, a rebar3 plugin for the generation of static validation modules in compile time has been also developed.



I will have to give this a try. I was in the market for a validation library!

1 Like