README

Just another library to handle Value Objects and prevent the bad habit of Primitive Obsession

Changelog

All notable changes to this project will be documented in this ChangeLog file.

Install

Require the vendor with Composer:

composer require david-garcia/value-object

Usage

Make sure you are loading the Composer autoload:

require 'vendor/autoload.php';

Don't forget adding the use statement for each one of the value objects you need to use:

// Example for StringValue
use DavidGarcia\ValueObject\Primitive\StringValue;

All value objects have a static create() method:

StringValue::create('qwerty');

The first argument is the value to be wrapped by the value object. The second argument allows you to statically cache the value object, so you can instantiate twice an object with the same value but the system will create it just once:

$stringValue1 = StringValue::create('qwerty', true);
$stringValue2 = StringValue::create('qwerty', true);

if ($stringValue1 === $stringValue2) {
    // TRUE
    // It's the same object, so it goes inside this conditional
}

$stringValue3 = StringValue::create('qwerty');
$stringValue4 = StringValue::create('qwerty');

if ($stringValue3 === $stringValue4) {
    // FALSE
    // Although they have the same value, the system has created two different objects
}

Null values always hold a null value:

// `NullValue` does not expect any argument
$nullValue = NullValue::create();

All value objects have a getValue() method to expose the value:

$stringValue = StringValue::create('qwerty');
$stringValue->getValue(); // Returns 'qwerty'

The StringValue value object and any other that extends from this one can use the __toString magic method to return the string value, as an alternative to the getValue() method:

$stringValue = StringValue::create('qwerty');
(string) $stringValue; // Returns 'qwerty'

All value objects (except NullValue) have an equals() method that compares the content of two value objects of the same type:

$stringValue1 = StringValue::create('qwerty', true);
$stringValue2 = StringValue::create('qwerty', true);

if ($stringValue1->equals($stringValue2)) {
    // TRUE
    // We ignore the fact that is a cached object, as we compare the value
}

$stringValue3 = StringValue::create('qwerty');
$stringValue4 = StringValue::create('qwerty');

if ($stringValue3->equals($stringValue4)) {
    // TRUE
    // We have a match for the values, so even if we handle two different objects,
    // their values are equal
}