Motivation

Why do you need Modddels ?

Let's say you want to model a Student object. The Student has a name, an age, and an email. You may create your class/data-class this way :

class Student {
  Student({
    required this.name,
    required this.age,
    required this.email,
  });

  final String name;
  final int age;
  final String email;
}

You will then need to validate the name, age and email in various parts of your app. The Student model will be used in different places : for example, a widget that displays a student profile, or a function addStudent(Student newStudent), etc...

There are several problems with this approach :

• Where should you validate the name, age and email ?

• After validation is done, how can you distinguish between a valid Student instance and an invalid one ?

• How can you ensure that valid Student instances are passed to functions or widgets that require them, and likewise, invalid instances are passed to those that specifically handle them?

• How to handle an invalid Student differently based on what field is invalid and why it's invalid, all this in various parts of the app ?

• If you have, for example, a widget that displays the email of a Student. How can you prevent any random string from being passed to the widget ?

All these problems (and more) can be resolved by using this package.

The Modddels package offers a way to validate your models and deal with its different states (valid, invalid...) in a type-safe and compile-safe way.

• 🔎 Self-Validation : Your models are validated upon creation. This way, you'll never deal with non-validated models.
• 🧊 Sealed class : Your model is a sealed class, which union-cases are the different states it can be (valid, invalid...). For example, Student would be a sealed class with union-cases ValidStudent and InvalidStudent.
• 🚨 Failures handling : Your model, when invalid, holds the responsible failure(s), which you can access anytime anywhere.
• 🔒 Value Equality and Immutability : All models are immutable and override operator == and hashCode for data equality.
• 🧪 Unit-testing : Easily test your models and the validation logic.

This package is NOT a data-class generator. It is meant to create models that are at the core of your app (If you use DDD or Clean architecture, those would be in the "domain" layer). Therefore, you are meant to create separate classes for things like json serialization, either manually or with tools like freezed and json_serializable (These classes are usually called "DataTransferObjects", "DTOs", or simply "models").