level-assoc

foreign key
associations
(hasMany, belongsTo, ...)
for leveldb


example

`` js
var sub = require('level-sublevel');
var level = require('level-test')();
var db = sub(level('test', { valueEncoding: 'json' }));

var assoc = require('level-assoc')(db);
assoc.add('hackerspace')
.hasMany('hackers', [ 'type', 'hacker' ])
.hasMany('tools', [ 'type', 'tool' ])
;
assoc.add('hacker').belongsTo('hackerspace');
assoc.add('tool')
.hasMany('usage', [ 'type', 'usage' ])
.belongsTo('hackerspace')
;

db.batch(require('./data.json').map(function (row) {
return { type: 'put', key: row.key, value: row.value };
}), ready);

function ready () {
assoc.get('sudoroom', function (err, room) {
console.log('SUDOROOM=', room);
room.hackers().on('data', function (r) {
console.log('HACKER', r.value)
});
});

assoc.get('8d9a83', function (err, tool) {
console.log('TOOL=', tool);
tool.usage().on('data', function (r) {
console.log('USAGE', r.value)
});
});
}
`

given this data.json in the database:

` json
[
{"key":"sudoroom","value":{"type":"hackerspace","name":"sudoroom"}},
{"key":"noisebridge","value":{"type":"hackerspace","name":"noisebridge"}},
{"key":"substack","value":{"type":"hacker","name":"substack","hackerspace":"sudoroom"}},
{"key":"maxogden","value":{"type":"hacker","name":"maxogden","hackerspace":"sudoroom"}},
{"key":"ioerror","value":{"type":"hacker","name":"ioerror","hackerspace":"noisebridge"}},
{"key":"mitch","value":{"type":"hacker","name":"mitch","hackerspace":"noisebridge"}},
{"key":"wrought","value":{"type":"hacker","name":"wrought","hackerspace":"sudoroom"}},
{"key":"mk30","value":{"type":"hacker","name":"mk30","hackerspace":"sudoroom"}},
{"key":"8d9a83","value":{"type":"tool","name":"3d printer","hackerspace":"sudoroom"}},
{"key":"ea7e66","value":{"type":"tool","name":"piano","hackerspace":"sudoroom"}},
{"key":"025452","value":{"type":"tool","name":"laser cutter","hackerspace":"noisebridge"}},
{"key":"yardena","value":{"type":"hacker","name":"yardena","hackerspace":"sudoroom"}},
{"key":"5cc709","value":{"type":"tool","name":"3d printer","hackerspace":"noisebridge"}},
{"key":"d06ab1","value":{"type":"usage","tool":"8d9a83","minutes":"45","user":"maxogden"}},
{"key":"2454c1","value":{"type":"usage","tool":"8d9a83","minutes":"20","user":"yardena"}},
{"key":"ec08ed","value":{"type":"usage","tool":"ea7e66","minutes":"14","user":"substack"}},
{"key":"61baab","value":{"type":"usage","tool":"025452","minutes":"8","user":"mitch"}}
]
`

the program prints:

`
SUDOROOM= { type: 'hackerspace',
name: 'sudoroom',
hackers: [Function],
tools: [Function] }
TOOL= { type: 'tool',
name: '3d printer',
hackerspace: 'sudoroom',
usage: [Function] }
HACKER { type: 'hacker', name: 'maxogden', hackerspace: 'sudoroom' }
USAGE { type: 'usage', tool: '8d9a83', minutes: '20', user: 'yardena' }
HACKER { type: 'hacker', name: 'mk30', hackerspace: 'sudoroom' }
USAGE { type: 'usage', tool: '8d9a83', minutes: '45', user: 'maxogden' }
HACKER { type: 'hacker', name: 'substack', hackerspace: 'sudoroom' }
HACKER { type: 'hacker', name: 'wrought', hackerspace: 'sudoroom' }
HACKER { type: 'hacker', name: 'yardena', hackerspace: 'sudoroom' }
`

methods

` js
var levelAssoc = require('level-assoc')
`

var assoc = levelAssoc(db)

Create a new assoc instance from a
sublevel-enabled
leveldb instance db.

assoc.get(key, cb)

Fetch a key from the database with cb(err, row).
row contains the underlying db.get() result but augmented with functions to
return streams for the has-many collections.

var t = assoc.add(name)

Create a new type association t for rows with a "type" field set to name.

t.hasMany(key, filterKey)

Create a streaming collection at key for foreign rows matching the string
array path filterKey.

t.belongsTo(key)

TODO. Currently a no-op.

install

With npm do:

`
npm install level-assoc
``

license

MIT