CODEWITHSUNDEEP
c#design-patternsdomain-driven-designrepository-patternddd-repositories
Arnold Zokas
Arnold Zokas

Reputation: 8580

What is the correct aggregate root?

I have the following data structure:

class Post
{
    public string Title { get; set;}
    public Category Category { get; set;}
}

Bearing in mind a post always belongs to one and only one category is my reasoning correct?

Upvotes: 2

Views: 776

Answers (2)

Adam Ralph
Adam Ralph

Reputation: 29956

How do you want to reference instances of Post? Is Post.Title a unique identifier for a Post? If so, then Post is a valid aggregate root and you should create a PostRepository which retrieves an instance of Post given it's Title.

Take the example of a car. A car must have a colour, but stating that the colour is the aggregate root just because a car cannot exist without one is the wrong thing to do. I want to reference a car independently given it's license plate number (which is independent of it's colour). The fact that it must have a colour is simply a feature of my car domain model which states that I cannot construct a car instance without supplying the colour.

Upvotes: 5

Chris Marisic
Chris Marisic

Reputation: 33128

I often cite this resource when it comes to aggregate root design considerations RavenDB - StackOverflow style voting with Live Projections. This addresses some of your key thought process and should show you why Category would be a VERY POOR aggregate root.

Upvotes: 1

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