How to model this domain? DDD - oop

Question

In the domain that i'm trying to model, there are 2 classes: ClothingType and TreatmentType
public class ClothingType : Entity<Guid>
{
public string Name { get; protected set; }
public ClothingType(Guid id, string name)
: base (id)
{
Name = name;
}
}
public class TreatmentType : Entity<Guid>
{
public string Name { get; protected set; }
public TreatmentType(Guid id, string name)
: base(id)
{
Name = name;
}
}
A ClothingType (t-shirt, pant, etc) support many kinds of TreatmentType's (wash, iron, etc). And one kind of TreatmentType can be supported by many ClothingType's. But, the price of a specified TreatmentType varies according to ClothingType.
Imagine two kinds of treatments: wash and iron. In t-shirts, washing costs $20, in pants costs $35, and so on. How to model this?
Thanks in advance.

Answer 1

Clothing type and Entity Type are probably values, rather than entities.
There might be a product catalog, or some analog to it, with query methods that take a clothing type and an entity type as inputs and provide a pricing estimate as an output. If you needed that pricing estimate in your domain logic, then you would likely achieve that via a domain service that allowed the model to access a recent copy of the product catalog to look up the pricing.

Answer 2

Check out Alberto Brandolini's Event Storming approach so you could discover the domain you're dealing with. Is billing part of your core bounded context?
If it's just a usual ecommerce product with a price, you should definetly start with defining ClothingType and TreatmentType as Value Objects. I'm no Java expert but in PHP it would look like this:
class Cloth {
/** #var ClothingType */
private $type;
/** #var TreatmentType[]|array */
private $treatments;
...
}
Also check the Money pattern cause it might come in handy when creating your ValueObjects.
I would suggest not diving into DDD (especially in the tactical phase) without a slight understanding of it's principles. At least try to read Vaughn's DDD Distilled.
EDIT: Giving it a second thought I would design more or less it like this:
class Treatment {
/** #var TreatmentId */
private $treatmentId;
/** #var TreatmentType */
private $type;
/** #var Money */
private $price;
//constructor, getters, etc.
public function modifyPrice(int $amount)
{
$this->price = new Money($amount);
}
}
class Cloth {
/** #var ClothType */
private $type;
/** #var Treatment[]|array */
private $treatments;
public function addTreatment(Treatment $aTreatment)
{
array_push($this->treatments, $aTreatment);
}
}