Awesome

Jǫrmungandr

Jǫrmungandr is a simple ORM, as in Object Redis Mapper. It enables very flexible creation of Ruby objects backed by a Redis database. It is kind of similar to Struct, but more dynamic. Model classes can be created like so:

Thing = Jormungandr.new

thing = Thing.new

Thereafter, objects essentially are their own little key-value stores, wrapped with some method_missing magic:

thing.foo = "bar"
thing.foo
  => "bar"

Similar magic is used for one-to-many mappings: If a method is called that is a pluralization of the name of a Model subclass (e.g. Thing), it returns all instances of that subclass that reference the object on which the method was called.

p = Person.new
thing1.person = p
thing2.person = p
p.things
  => [thing1, thing2]

Features

• When the Jormungandr class loads, the associated Redis database is scanned for hkeys beginning with "Jormungandr.". From each of these hashes, a corresponding Ruby object is created.

• The Ruby object representing a model instance is very thin. It has one instance variable, @id, which corresponds to the Redis hashkey where the object is persisted.

• Attribute accessors are set up with method_missing magic, so there is no need to declare new attributes. It is up to the programmer to keep track of what attributes are used.

• The model objects will naively store attributes of any name. Every object is in effect its own little key-value store, with every key being a valid method of the object itself.

• In a Redis hash representing a model object, the values are Ruby objects serialized with Marshal.

• If the Sinatra module is loaded, a REST API is created through which the model objects can be accessed and manipulated using the standard HTTP verbs. Also, some admin views are created. (NOTE: Not yet merged into public repo!)

• If a method is called that is a pluralized form of a Model subclass, it returns all instances of this subclass that references the instance on wich the method was called (one-to-many relations).

Example of usage

$ irb -r ./jormungandr
> Person = Jormungandr.new
=> nil
> p = Person.new
=> #<Person:0x101115740 @id=0> 
> p.name = "Martin"
=> "Martin"
> p.age = 28
=> 28 
> exit
$ irb -r ./jormungandr
> Person.all
=> [#<Person:0x101125dc0 @id=0>] 
> Person.all.first.name
=> "Martin"
> Person.all.first.age
=> 28

Note that the Person class is created only once. In the second irb session, Jǫrmungandr creates it when it finds a reference to it in the database.