https://github.com/mrgravity817/cosmic-clojure
Learn how to build your Clojure application using TDD, DDD techniques.
https://github.com/mrgravity817/cosmic-clojure
clojure domain-driven-design test-driven-development
Last synced: 10 months ago
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Learn how to build your Clojure application using TDD, DDD techniques.
- Host: GitHub
- URL: https://github.com/mrgravity817/cosmic-clojure
- Owner: MRGRAVITY817
- Created: 2024-09-21T14:27:13.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-10-27T02:16:54.000Z (about 1 year ago)
- Last Synced: 2025-04-02T22:44:02.011Z (10 months ago)
- Topics: clojure, domain-driven-design, test-driven-development
- Language: Clojure
- Homepage:
- Size: 43 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Cosmic Clojure
Here we learn how to build your Clojure application using TDD, DDD techniques.
This repo follows the learning path of the book [Cosmic Python](https://www.cosmicpython.com/) by Harry J.W. Percival and Bob Gregory. The difference is that unlike the book, I've writted the code in Clojure, not in Python.
## Chapter 1: Domain modeling
### Setup
Create a new Clojure project with the following command:
```bash
$ mkdir cosmic-clojure
$ cd cosmic-clojure
$ touch deps.edn
```
The chapter needs some basic libraries:
- to write & run tests: `cognitect.test-runner`
- to modeling the domain data: `malli`
Copy and paste the following code to `deps.edn`:
```clojure
{:aliases {:test {:exec-fn cognitect.test-runner.api/test,
:extra-deps {io.github.cognitect-labs/test-runner
{:git/sha "dfb30dd", :git/tag "v0.5.1"}},
:extra-paths ["test"],
:main-opts ["-m" "cognitect.test-runner"]}},
:deps {metosin/malli {:mvn/version "0.16.4"},
org.clojure/clojure {:mvn/version "1.12.0"}},
:paths ["src"]}
```
Now you're good to go!
### Summaries
- **Domain** is the problem you're trying to solve. Hence the **domain model** is the structure of the data that would be used to solve the problem.
- In Clojure you can use any schema libraries to build value objects - e.g. malli, schema, etc - since the data is immutable by default.
- When it comes to entities, it might be tempting to override default operators like `==` (for equality checking) and `>` (for comparison and sorting).
But operator overriding is not a good idea in Clojure - just create a simple function for each case like `batch-eq?` or `batch-gt?`.
## Chapter 2: Repository Pattern
### Setup
From this chapter, we'll need some kind of database to store our data. I've chosed the [XTDB](https://github.com/xtdb/xtdb), for the sake of it being well adopted among Clojure ecosystem.
For using XTDB within our project, add those dependencies to `deps.edn`:
```clojure
{:deps {;; ...
;; xtdb-api for the main public API, for both remote-client and in-process nodes
com.xtdb/xtdb-api {:mvn/version "2.0.0-b1"}
;; xtdb-http-client-jvm for connecting to a remote server
com.xtdb/xtdb-http-client-jvm {:mvn/version "2.0.0-b1"}
;; xtdb-core for running an in-process (test) node (JDK 21+)
com.xtdb/xtdb-core {:mvn/version "2.0.0-b1"}}
;; JVM options required for in-process node
:aliases {;; ...
:dev {:jvm-opts ["--add-opens=java.base/java.nio=ALL-UNNAMED"
"-Dio.netty.tryReflectionSetAccessible=true"]}}}
```
We'll use `dev` alias to run our dev repl, running with in-process XTDB node. Run it with the following command:
```bash
$ clj -A:dev
```
Then you can now jack into this repl from your IDE.