modella-sublevel

Modella plugin to attach a model to a sublevel-based backing store, with optional secondary indexing.

Usage

``js
var sublevel = require('modella-sublevel')

var MyModel = model('MyModel')
.use(sublevel)

// primary key field required (defaults to id or _id attr per modella API
.attr('mykey', {
primaryKey: true
})

// unindexed attribute
.attr('somefield', {
defaultValue: 'xxx'
})

// explicitly indexed field
.attr('indexedfield', {
index: true
})

// unique fields are implicitly implicitly indexed to verify uniqueness
.attr('uniquefield', {
unique: true
})

// model initialized, but saving instances will throw until store is attached
var model = new Model({
mykey: 'a',

// unique fields are inherently required: true
uniquefield: 'foo'
})

model.save(function(err, model) {
err.message === 'No store available'
})
`

$3

`js
// some time later, assuming db is in scope...
var store = db.sublevel('MyModel')

// attach new sublevel as backing store for our model
MyModel.attach(store)

// now we can save model instances
model.save(function (err, model_) {
// no error this time
err == null

// callback is invoked with the same instance of model
model_ === model
})
`

$3

`js
// the backing store is made available on the store key
MyModel.store === store

// store methods are overriden to do model creation/validation
myStore.put('b', {
// id will be set to primaryKey field defined by model
uniquefield: 'bar'
}, function (err, record) {
// store.put overridden to return created JSON record
record.key === 'a'

// this will include any attributes generated by model instantiation
record.somefield === 'xxx'
})
`

$3

`js
// modella API extended with some static convenience methods
MyModel.create({
mykey: 'c',
uniquefield: 'baz'
}).save(err, model) {
// again, result of save is a model instance, which we can manipulate
model.somefield('yyy')

model.save(function (err) {
// our changes are now persisted
})
})

// convenient static methods are available for interfacing with the store
MyModel.add({
// ensures key is new
mykey: 'd',
uniquefield: 'quux'
})

// query by primary key (if createReadStream available on sublevel)
Model.query({ gt: 'b' }).on('data', function (model) {
// invoked with model instances
model.primary() >= 'b'
})

// query on a secondary index explicitly (if supported by sublevel)
Model.query.uniquefield({ gt: 'bar' }).on('data', function (model) {
model.uniquefield() > 'bar'
})

// observe changes on an indexed attribute (if createLiveStream avaialable)
Model.tail.indexedfield().on('data', function (data) {
if (data.type !== 'del') {
// data.model.get('indexedfield')
}
})
`

$3

The attach method can be called without a store reference to detach store from model:

`js
OtherModel.attach()
OtherModel.store === undefined
``

When detaching, any methods overwritten on the backing store instance will be replaced with their original versions.