12 lines
3.7 KiB
Markdown
12 lines
3.7 KiB
Markdown
# db-subclass-to-dto
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This is a workspace for creating three exercises.
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One exercise is about exploring a repository using prompts for a coding agent to create Mermaid and PlantUML diagrams. We're focusing on class diagrams and sequence diagrams to get an idea of what is going on. We use the starting point of the second exercise for this.
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The second exercise is factoring out domain objects, domain entities, from a structure that is previously subclass-based. So say you use a structure like active records or Entity Framework where you have an active record class and your domain class subclasses from the active record class which gives you maybe some nice things like find by an attribute. And then you can quite quickly — so these are straight-offs — you can quite quickly structure an application while it's also persisted. So you can say, "I want to have a customer, I want to have an order. And oh yes, I'm doing this for a webshop." So you have objects, relations, attributes, and you can all easily save them in your database. And this is fine when your application is small and you're just starting out. It allows you to very quickly scaffold an application. But it can become painful when your data doesn't have the right shape for it. So performance is slow. So at some point as your application grows, you probably want to be more deliberate in how you start.
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The second exercise is factoring out domain classes from a database inheritance structure. So we start with a couple of domain classes and some relations. Then we pre-deliver some classes that we already created and we demo it. As we have some domain classes, we create a mapping for writing and reading a domain class. And we make sure that running the existing tests against the fake database that we have for the exercise is really slow. The sequence diagrams that we make in the first exercise will come in handy. Because in order to do this, you do start wondering how does this web application find a client? How can we see clients? How can we create an order? And what happens once the flow through the application as we do this? You sort of need to understand this to choose the kind of mapping that you use. So we are going to reuse the analysis we did in the first exercise in the second exercise.
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The third part is a spike in creating an extract method refactoring using Roslyn, the C# static analysis tooling that comes as part of C# more or less. It's an additional NuGet download but yeah it is quite good. So this is a simple command line that allows you to specify the name of a file, the starting line and the end line and it will give you an analysis of dependencies inside the method that you need to decide which things could lend itself to extracting to a method, what the parameters could be and what the return value could be. This is work in progress so this is not something to share with participants but it is part of a flow where you first you iterate and you prompt, you create codes then maybe you extract things into a skill or you prompt for a diagram of some kind. You go, ah I often seem to make sequence diagrams. Okay, can we make something deterministic to create these sequence diagrams so it's faster and more reliable? Or in my case I don't like, well I like the extract method stuff in JetBrains IDEs but I need to do some steps before to find the parameters, extract variables, extract the methods with these variables as parameters then inline the variables again and I was wondering if I could do that more smoothly in the flow with a coding agent. That also means that going further I could do things like forbid extracted methods from having Async in all parts, but see if we can extract parts without side effects first.
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