IVH Model

Models for JavaScript

Super lightweight and largely inspired by ExtJS data models.

IvhModel allows you to convert value objects into robust, immutable models. It protects your app from API changes and provides a nice abstraction layer for business entities.

Getting Started

Install with npm:

npm install --save ivh-model

Now get IvhModel via commonjs or es6 imports:

const IvhModel = require('ivh-model')

// or

import IvhModel from 'ivh-model'

Usage

Typical use invovles extending IvhModel and declaring your model's fields. All model constructors accept a single options hash. For example:

// Basic usage
class Thing1 extends IvhModel {
  // All model attributes are found by looking up options of the same name. Note
  // this is an accessor method.
  static get fields() {
    return [
      'id',
      'alias',
      'power'
    ]
  }
}

const opts = {
  id: 123,
  alias: 'Vageta',
  power: 550
}

// Using "new"
const t1 = new Thing1(opts)

// Using IvhMode.create
const t2 = Thing1.create(opts)

// IvhMode.create also works when handed off to e.g. Array.prototype.map
const models = [opts, opts].map(IvhModel.create)

t1.get('alias')
// --> 'Vageta'

t2.get('power')
// --> 550

// Fancy fields
class Thing2 extends IvhModel {
  static get fields() {
    return [
      // Fields can be pulled from options of the same name...
      'id',

      // .. or somewhere else entirely...
      {
        name: 'alias',
        mapping: 'attributes.alias'
      },

      // ... it's ok if a value is missing, but...
      {
        name: 'missing',
        mapping: 'attributes.from.somewhere.missing'
      },

      // ... you may want to set a default value...
      {
        name: 'power',
        defaultValue: 9001
      },

      // ... or even use a calculated/virtual field.
      {
        name: 'id_alias',
        convert: (opts, model) => {
          return `${opts.id}_${model.get('alias')}`
        }
      }
    ]
  }
}

const t3 = Thing2.create({
  id: 456,
  attributes: {
    alias: 'Goku',
    unused: 'foobar'
  }
})

t3.get('alias')
// --> 'Goku'

t3.get('missing')
// --> undefined

t3.get('unused')
// --> undefined

t3.get('power')
// --> 9001

t3.get('id_alias')
// --> '123_Goku'

You may want to extend the base IvhModel centralize data access:

class MyBase extends IvhModel {
  static fetch(where) {
    return fetch(this.endpoint, {
        body: JSON.stringify(where)
      })
      .then(resp => resp.json().map(this.create))
  }
}

class Thingy extends MyBase {
  static endpoint = '/place/to/get/thingies'

  static get fields() {
    return ['id', 'alias']
  }

  watsDat() {
    return 'a senzu bean'
  }
}

Thingy.fetch({alias: 'Go*'}).then(/* ... */)

Thingy.create({id: 1, alias: 'Goku'}).watsDat()
// --> 'a senzu bean'

You can set model attributes. This will return a new model with the updated values rather than mutating the given model.

const t1 = Thing1.create({
  id: 'foo',
  alias: 'Foo',
  power: 6
})

const t2 = t1.set('power', 11)

t1.get('power')
// --> 6

t2.get('power')
// --> 11

After setting all those values you might want to save your changes back to a database somewhere.

class SillyThing extends IvhModel {
  static get fields() {
    return [
      'id',
      {
        name: 'alias',
        mapping: 'attributes.Label'
      }, {
        name: 'power',
        defaultValue: 9001
      }
    ]
  }
}

let s1 = SillyThing.create()
s1 = s1.set('alias', 'Goku')
s1.extract()
// --> {power: 9001, attributes: {Label: 'Goku'}}

Sometimes you need to massage your extracted content.

class SillyThing extends IvhModel {
  static get fields() {
    return [
      'id',
      {
        name: 'alias',
        mapping: 'attributes.Label'
      }, {
        name: 'power',
        defaultValue: 9001
      }
    ]
  }

  static extract(extractedData, sillyModel) {
    const alias = sillyModel.get('alias')
    const power = extractedData.power
    extractedData.prettyPrint = alias + ' ' + power
  }
}

let s1 = SillyThing.create()
s1 = s1.set('alias', 'Goku')
s1.extract().prettyPrint
// --> 'Goku 9001'

You can chain set calls but sometimes it's easier to just create a new model from scratch using model attributes:

class FancyThing extends IvhModel {
  static get fields() {
    return [{
      name: 'alias',
      mapping: 'foo.bar.barus'
    }]
  }
}

const fancy = FancyThing.createSet({
  alias: 'P Fancy'
})

fancy.get('alias')
// --> 'P Fancy'

fancy.extract()
// --> {foo: {bar: {barus: 'P Fancy'}}}

Note that fields with a convert function will not be extracted.

See the tests and comments in lib/index.js for more examples.

License

MIT