Aggregate Design: Using Invariants as a Guide

How do you compose an aggregate? For me aggregate design involves understanding the invariants. Invariants are business rules that must always be consistent.

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0:00 Intro
1:32 Aggregates
2:11 Invariants
3:33 Code Example
7:38 Recommendations

#softwarearchitecture #softwaredesign #domaindrivendesign

[skipodap]

"Don't expose domain objects that can't enforce the business rules". That closing sentence was brilliant. Thanks for the vids

[RobLang]

Been using DDD for over 10 years, popped in for a new take and although this confirmed what I knew, I just applaud and say it was explained brilliantly!

[technicaltorch]

I rarely ever comment on YouTube videos, but this is well deserved.

You're concise and straight to the point, fantastic content. I struggled to find video resources on DDD and resorted to books, I wish this content was here when I first started learning. Please keep doing what you're doing!

[xbmcme]

Really like the concrete examples. It's really hard to imagine a technical implementation of different concepts that I've never seen before in my life. Thanks for taking the time to make these videos. They are super helpful!

[secondry]

Since watching your videos my code quality has improved 10-fold and performs 10x better, not an exaggeration. Keep it up, loving the videos!

[kozer]

I'm crying of joy!!! Amazing channel. What I was looking for to grasp ddd more!

[hesamkashefi]

Very good explanation. For me, the harder problem is how to find aggregate roots and their boundaries in a real-world project, it would be a very helpful video if you could make it for us.

[ToeShimmel]

Your video's are fantastic. I keep coming back and they make me a much better developer. Thanks so much. You deserve more views!

[NomadicBrian]

Excellent presentation. Walked away with a much clearer understanding of Aggregates.

[williamsbotchway]

Hi Dereck i am new to ddd but i have question on the video. Since u are passing a collection of stops to the constructer of the shipment aggregate, it means clients other than the shipment aggregate can call both the arrive and isComplete methods thereby resulting in inconsistent state, by passing the rules defined in the shipment aggregate? Does this means a refinement of what is needed to enforce the invariant is needed? Pls answer on this. Also one general rule is that entities inside an aggregate can only be reference by other aggregate by holding a transient copy of these entities. I think passing a collection of stops as shown in the videos violate this general rule. however domain services can be used to defined previousStopAreNotDeparted and used as client in stop which should be treated as aggregate. If this approach is corrected should we have two distinct aggreagete for PickupStop and DeliveryStop. Again i am a novice to ddd so please advice. Thank u.

[victortodoran]

Ok, this one I had to watch three times, but I really enjoyed it in the end.
This was a well picked example, the implementation is pretty nifty and smart and some good points were made.
I did not care for what I supose is ddd lingo, but I gues that is on me to learn.
Thanks for taking the time.

[michaelwong]

That's clearly explained! Wish I have learnt this earlier.

[vakul_k]

Inside the stop class. We have sequence as primitive. Should we create it as a value type? From what I have seen DDD says we should not have primitives

[JohnnysaidWhat]

These videos are where you go when you fight the final boss of EDD. So good but so technical.

[Eugene.g]

I wish my code was that clean and readable

[alfonsdeda]

Hi Derek, i use ef core for my database and in one service class i should update two entities in the same transaction, for the ofher entity i already have the independent service that could the operation that i would need but it must be done in the same transaction, should i implement the unit of work pattern or is ok to use directly the dbcontext even for an operation that is already implemented separately?

I hope it is clear.
Thanks in advance.

[snowglider]

@CodeOpinion why you didn't use state machine ?

[thedacian]

Spotting boundaries is a complicated stuff, and DDD in general which leads to domain experts/analists comitmment.But what should we do if business people are not too cooperant?Thanks

[ivanmiroshnichenko]

As far as I understood, if I have a 'manager' class which has a couple of methods such as 'Run()' something or 'Stop()' something is an aggregate class, isn't it?

[lost-prototype]

Great video! A quick question...

Do you ever create extension methods on generic collection types of your domain models to represent certain filters or operations?