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Generate nested namespaced keys for key-value databases.

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README.md

Nest

Object Oriented Keys for Redis.

Description

If you are familiar with databases like Redis and libraries like Ohm you already know how important it is to craft the keys that will hold the data.

>> redis = Redis.new
>> redis.sadd("event:3:attendees", "Albert")
>> redis.smembers("event:3:attendees")
=> ["Albert"]

It is a design pattern in key-value databases to use the key to simulate structure, and you can read more about this in the case study for a Twitter clone.

Nest helps you generate those keys by providing chainable namespaces that are already connected to Redis:

>> event = Nest.new("event")
>> event[3][:attendees].sadd("Albert")
>> event[3][:attendees].smembers
=> ["Albert"]

Usage

To create a new namespace:

>> ns = Nest.new("foo")
=> "foo"

>> ns["bar"]
=> "foo:bar"

>> ns["bar"]["baz"]["qux"]
=> "foo:bar:baz:qux"

And you can use any object as a key, not only strings:

>> ns[:bar][42]
=> "foo:bar:42"

In a more realistic tone, lets assume you are working with Redis and dealing with events:

>> events = Nest.new("events")
=> "events"

>> id = events[:id].incr
=> 1

>> events[id][:attendees].sadd("Albert")
=> "OK"

>> meetup = events[id]
=> "events:1"

>> meetup[:attendees].smembers
=> ["Albert"]

Supplying your existing Redis instance

You can supply a Redis instance as a second parameter. If you don't, a default instance is created for you:

>> redis = Redis.new
=> #<Redis::Client...>

>> users = Nest.new("users", redis)
=> "users"

>> id = users[:id].incr
=> 1

>> users[id].hset(:name, "Albert")
=> "OK"

Nest objects respond to redis and return a Redis instance. It is automatically reused when you create a new namespace, and you can reuse it when creating a new instance of Nest:

>> events = Nest.new("events", meetup.redis)
=> "events"

>> events.sadd(meetup)
=> true

>> events.sismember(meetup)
=> true

>> events.smembers
=> ["events:1"]

>> events.del
>> true

Nest allows you to execute all the Redis commands that expect a key as the first parameter. Think of it as a curried Redis client.

Differences with redis-namespace

redis-namespace wraps Redis and translates the keys back and forth transparently.

Use redis-namespace when you want all your application keys to live in a different scope.

Use Nest when you want to use the keys to represent structure.

Tip: instead of using redis-namespace, it is recommended that you run a different instance of redis-server. Translating keys back and forth is not only delicate, but unnecessary and counterproductive.

Differences with Ohm

Ohm lets you map Ruby objects to Redis with little effort. It not only alleviates you from the pain of generating keys for each object, but also helps you when dealing with references between objects.

Use Ohm when you want to use Redis as your database.

Use Nest when mapping objects with Ohm is not possible or overkill.

Tip: Ohm uses Nest internally to deal with keys. Having a good knowledge of Nest will let you extend Ohm to suit your needs.

Installation

$ gem install nest

License

Copyright (c) 2010 Michel Martens & Damian Janowski

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.

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