https://github.com/jerems/flow
Barebones dataflow in clojure(script)
https://github.com/jerems/flow
clojure clojurescript
Last synced: 2 months ago
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Barebones dataflow in clojure(script)
- Host: GitHub
- URL: https://github.com/jerems/flow
- Owner: JeremS
- License: epl-1.0
- Created: 2017-07-20T12:34:56.000Z (almost 8 years ago)
- Default Branch: master
- Last Pushed: 2017-07-20T23:17:02.000Z (almost 8 years ago)
- Last Synced: 2025-03-06T17:18:48.684Z (2 months ago)
- Topics: clojure, clojurescript
- Language: Clojure
- Size: 18.6 KB
- Stars: 4
- Watchers: 3
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# flow
[](https://clojars.org/jeremys/flow)
This library provides a simple dataflow engine. It is created with
om-next's default db format in mind. However since this db format is
just Clojure data...
## Usage
Here is part of the example used in the devcards.
You have a db that looks like this:
```clojure
(def init-data
{:parameters {:turnover 1000}
:charges [[:charges/by-id 1]]
:charges/by-id {1 {:id 1 :name "Marketing" :cost 100}}})
```
You want to have reactions that add the charges and compute what is
left of the turnover after these charges.
You start by defining reactions:
```clojure
(defn compute-total-charges
[{:keys [charges-table]}]
(transduce (map :cost)
+
(vals charges-table)))
(def total-charges
{:name :total-charges
:srcs {[:charges/by-id] :charges-table}
:dest [:computed :total-charges]
:fn compute-total-charges})
(defn compute-result
[{:keys [t cs]}]
(- t cs))
(def result
{:name :result
:srcs {[:computed :total-charges] :cs
[:parameters :turnover] :t}
:dest [:computed :result]
:fn compute-result})
```
Then you build a dataflow system:
```clojure
(require '[flow.core :as flow]
(def system
(-> flow/empty-system
(flow/add-reactions [total-charges result])
(flow/ready-system)))
```
and use it
```clojure
(def db (flow/execute-system init-data system #{flow/whole-db}))
db
;=>
{:parameters {:turnover 1000},
:charges [[:charges/by-id 1]],
:charges/by-id {1 {:id 1, :name "Marketing", :cost 100}},
:computed {:total-charges 100, :result 900}}
(def db2
(-> db
(assoc-in [:charges/by-id 2] {:id 2 :name "travel expenses" :cost 200})
(flow/execute-system system #{[:charges/by-id 2]})))
db2
;=>
{:parameters {:turnover 1000},
:charges [[:charges/by-id 1]],
:charges/by-id
{1 {:id 1, :name "Marketing", :cost 100},
2 {:id 2, :name "travel expenses", :cost 200}},
:computed {:total-charges 300, :result 700}}
```
The `execute-system` function takes 3 arguments:
- a db
- a system
- a set of paths indicating where the change happened so that only
the relevant reactions are run.
There is more information in the devcards.
## Running devcards
Clone this repo then:
```
lein run -m clojure.main scripts/repl.clj
```
Open [this link](http://localhost:3449/devcards.html).
## License
Copyright © 2017 Jérémy Schoffen
Distributed under the Eclipse Public License (see LICENSE).