valid_value_objects 0.1.0-nullsafety.1

A new Flutter package project.

Valid value objects

Dart package to create immutable and validated value objects.

Table of contents

• Overview
• Setup
• Usage
• Serialization

Overview

You might be familiar with Value Objects from DDD concepts. Value Objects provides

• immutability
• type safety
• code readability
• validation
  • Objects are only instantiated if input parameter(s) are valid.
  • Making invalid value objects unrepresentable.

The package provides the following value objects:

• BoundaryDateTime
• EmailAddress
• IPAddress
• ISBN
• Name, FirstName, MiddleName, LastName
• Password
• PhoneNumber
• UniqueId

Note: Create your own value object by extending ValueObject class

Setup

Import it in your pubspec.yaml under dependencies

dependencies:
  valid_value_objects: ^0.1.0

Install it with pub get or flutter pub get

Import it in your dart files

import 'package:valid_value_objects/valid_value_objects.dart';

Usage

Some examples on how to create value objects.

Possible expections at object creation:

• RequiredValueException
• InvalidValueException
• TooShortValueException
• TooLongValueException

Note: All of the above exceptions are instance of ValueException.

Object creation examples:

EmailAddress

EmailAddress instantiation:

try {
  EmailAddress e = EmailAddress('[e-mail]');
} on RequiredValueException {
  // happens if param is null or empty
} on InvalidValueException {
  // happens if param doesn't match regex
}

// OR handle all exception at once:

try {
   EmailAddress e = EmailAddress('[e-mail]');
} on ValueException catch (e) {  
  // catches all value exceptions
  print(e.invalidValue);
  print(e.code);
  print(e.message);
}

Password

You may want to configure the default password requirements.

It can be done like this:

Password.minChar = ...;
Password.maxChar = ...;
Password.mustContainUpperChar = ...;
Password.mustContainNumeric = ...;
...

Or:

Password.setRequirements(
  minChar: 10,
  maxChar: 50,
  mustContainLowerChar: false,
  mustContainNumeric: false,
  mustContainUpperChar: false,
  mustContainSpecialChar: false,
);

Password instantiation:

try {
  Password psw = Password('xzY12&#eA');
} on RequiredValueException {
  ...
} on TooShortValueException {
  ...
} on TooLongValueException {
  ...
} on InvalidValueException {
  ...
} 

Serialization

Above validation and type safety every value object provides a toJson and fromJson method. By that fact, storing them in a NoSQL database is easy. The package is compatible with json_serialization package, but the package on it's own does not depend on it.

Costumize the key fields if required. Every value object has a static key field which are used by toJson and fromJson functions.

Default keys:

• EmailAddress --> "email"
• Name --> "name",
• FirstName --> "firstName",
• MiddleName --> "middleName",
• LastName --> "lastName"
• IPAddress --> "ip"
• ISBN --> "isbn"
• Password --> "password"
• PhoneNumber --> "phone"
• UniqueId --> "id"

Finding a key in a nested Map object? No problem.

const simpleMap = {'email' : '[e-mail]'};
const nestedMap = {
  'person' : {
    'contact' : {
      'phone' : '...',
      'email' : '[e-mail]',
    },
  },
};

EmailAddress.fromJson(simpleMap) == EmailAddress.fromJson(nestedMap) // true

Check the example folder for more example and clarification.