Model lookup objects as Entities or Value Objects?

[Naresh Bhatia]

Example

Entity: Office

{

    officeId: Identifier,

    countryCode: String

    ...

}

Lookup object: Country

Values (persisted in a table):

    { code: "AL", name: "Albania"},

    { code: "AG", name: "Antigua and Barbuda"},

    ...

In this example, the Office entity embeds a country code to describe it's location. Country feels like a value object, it is immutable object, it's a conceptual whole, it is completely replaceable. However value objects shouldn't have an identity, but I am using country code as its identity. What's the right way to think about this?

Other Examples

ExpenseItem embeds an expenseTypeCode

Task embeds a taskTypeCode

[Manuel Rascioni]

Being an Entity or a Value Object isn't absolute.

A Country maybe is an entity in a bounded context, and a value object in another. The same for your examples, when you create a new task type it is an entity, but when you create a Task and assign it a TaskType it is a value object for the Task entity, the task use it as a whole.

Using soft reference you will use just the CountryCode to reference a country in an entity, this is because in your entity you care about just what country is not its internal, that belongs to another context. 

[Naresh Bhatia]

Awesome! Thanks for clarifying, Manuel. So, as I understand it, CountryCode itself is a value (i.e. value object) and that's all the Office entity cares about. Country itself is a entity, perhaps in another bounded context.

[oguzh4n]

http://www.jefclaes.be/2013/05/accidental-entities-you-dont-need-that.html

11 Mayıs 2015 Pazartesi 10:31:51 UTC-4 tarihinde Naresh Bhatia yazdı:

[Naresh Bhatia]

Good read. Thank you!