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https://github.com/xsc/claro

Powerful Data Access for Clojure
https://github.com/xsc/claro

dataloader datasources infinite-trees

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Powerful Data Access for Clojure

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README 

        
# claro



__[Documentation](http://xsc.github.io/claro/)__ | __[Guides](doc)__



__claro__ is a library that allows you to streamline your data access, providing

powerful optimisations and abstractions along the way.



[![Build Status](https://travis-ci.org/xsc/claro.svg?branch=master)](https://travis-ci.org/xsc/claro)

[![Clojars Artifact](https://img.shields.io/clojars/v/claro.svg)](https://clojars.org/claro)

[![codecov](https://codecov.io/gh/xsc/claro/branch/master/graph/badge.svg)](https://codecov.io/gh/xsc/claro)



It is inspired by [muse][muse] and heavily influenced by [GraphQL][graphql].



claro requires Clojure ≥ 1.7.0.



[muse]: https://github.com/kachayev/muse

[graphql]: http://graphql.org/



## Features



claro is designed to be flexible and extensible. It'll make your data access

more elegant, efficient and testable, providing things like:



- __batched resolution__ of similar entities,

- automatic __caching__ of already known resolution results,

- __engine middlewares__ to hook into the resolution logic, allowing e.g.

  generic cache or circuit breaker implementations,

- pluggable __resolution strategies__ in the form of `Resolvable` selectors,

- an exchangeable __deferred implementation__, defaulting to

  [manifold][manifold],

- and pre-built middlewares for __data source mocking__, introspection and

  result transformation.



[manifold]: https://github.com/ztellman/manifold



## Quickstart



Data access is defined within records implementing the `Resolvable` interface.

Note that they can always produce more resolvables:



```clojure

(require '[claro.data :as data]

         '[manifold.deferred :as d])



(defrecord Person [id]

  data/Resolvable

  (resolve! [_ env]

    (d/future

      (fetch-person! (:db env) id)))

  data/Transform

  (transform [_ {:keys [friend-ids] :as person}]

    (assoc person :friends (map #(Person. %) friend-ids))))

```



Blindly resolving an infinite tree like this is usually not a good idea – but

claro offers _tree projections_ you can use to describe abstract transformations

of infinite structures:



```clojure

(require '[claro.projection :as projection])



(def person-with-friend-names

  {:id      projection/leaf

   :name    projection/leaf

   :friends [(projection/extract :name)]})

```



And here we go:



```clojure

(require '[claro.engine :as engine])



(engine/run!!

  (-> (->Person 1)

      (projection/apply person-with-friend-names)))

;; => {:id 1, :name "Sherlock Holmes", :friends ["Dr. Watson", "Ms. Hudson"]}

```



## Related Projects



| Library | Description |

|:------- |:----------- |

|[alumbra][alumbra]|GraphQL implementation on top of claro|

|[claro.circuit-breaker][claro-cb]|Circuit-breaker middleware based on [resilience4j][r4j]|



Feel free to open a pull request to add your project to this table.



[alumbra]: https://github.com/alumbra/alumbra

[claro-cb]:https://github.com/xsc/claro.circuit-breaker

[r4j]: https://github.com/resilience4j/resilience4j



## Documentation



1. [Basic Resolution](doc/00-basics.md)

2. [Projections](doc/01-projection.md)

3. [Advanced Projections](doc/02-advanced-projection.md)

4. [Engine](doc/03-engine.md)

5. [Testing & Debugging](doc/04-testing-and-debugging.md)

6. [Implementation Notes](doc/99-notes.md)



All these topics are also available in claro's [auto-generated

documentation][codox].



[codox]: http://xsc.github.io/claro/



## Contributing



Contributions are always welcome. Please take a look at the [Contribution

Guidelines](CONTRIBUTING.md) for a quick overview of how your changes can best

make it to master.



## License



```

MIT License



Copyright (c) 2015-2017 Yannick Scherer



Permission is hereby granted, free of charge, to any person obtaining a copy

of this software and associated documentation files (the "Software"), to deal

in the Software without restriction, including without limitation the rights

to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

copies of the Software, and to permit persons to whom the Software is

furnished to do so, subject to the following conditions:



The above copyright notice and this permission notice shall be included in all

copies or substantial portions of the Software.



THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

SOFTWARE.

```