Aggregate Design: Using Invariants as a Guide 

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

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!

I rarely ever comment on RU-vid 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!

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!

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

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

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

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

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.

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

🙏 thanks for your great work.

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.

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

I wish my code was that clean and readable

Thanks!

Thanks

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?

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

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.

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?

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

i have a quick question around the Stop classes, in terms of other stop information, location, opening times etc, would you have another, fuller entity/aggregate? and if the shipment required things like opening times for its business logic (eg to check its open on the shipment day), how would you do this? would you load the full entity/aggregate and pass this information in as part of the command or have i missed a concept?

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.

@CodeOpinion why you didn't use state machine ?

Instead of throwing exceptions on rule violations, is there any harm to make Shipment expose a single function, Advance(), which decides which stop to advance and how to advance (i.e. which Stop method to call) based on their states? If this over-simplified interface guarantees enforcing business rules, wouldn't these exceptions be unnecessary burden on Shipment consumers and tests?

Even with the Shipment aggregate root, the PickupStop and DeliveryStop classes still have public methods which can change the statuses independently. How to solve this? Thanks!

Didn’t you say that an anemic domain model is fine if you know it is?

isn't this somehow related to state machines?

Hey Derek, can you make these videos private and charge bit money? otherwise junior developers gonna catch up so quickly, we need our job to be safe 😂

why didn't i found this early so i don't have to refactor my code :(

The example is too complicated. It would have been better to pick up a simpler example to illustrate... I mean, after all the idea was to teach about aggregation right? Why make everything more confuse with deliveries, stops, shipment? Thanks anyway..

I have a question about these three status: InTransit, Arrived and Departed. They are related to Pickup and also to Delivery, okay? I'll improve my question with an example to see if I understood it well. Let's say that I ordered a pizza at my house. So the order has been processed and the pizza is ready to be delivered to my house. So the food app has a delivery person responsible for delivering to my house, which, in turn, needs to go to the restaurant to pick up the food and then take it to my house. With this example there are several status changes. Which of the two scenarios is what the video is trying to say? Or is it another? (Note that I may have misunderstood.) First scenario: - Delivery guy going to the restaurant - Status changed to InTransit - Delivery guy took my food - Status changed to Arrived - Delivery guy left with my food - Status changed to Departed - Deliverer is on the way - Status changed to InTransit - Deliver arrived at destination - Status changed to Arrived - Delivery person successfully dropped off the food - Status changed to Departed Second scenario: - Delivery guy going to the restaurant - Status changed to InTransit - Delivery guy got my food - Status not changed [InTransit] - Delivery guy left with my food - Status not changed [InTransit] - Deliverer is on the way - Status not changed [InTransit] - Deliver arrived at destination - Status changed to Arrived - Delivery person successfully dropped off the food - Status changed to Departed