Class-config-base NPM

class-config-base

The base class of a configuration class which configures a interfacial class.

Install

npm install class-config-base

Load this module

For Node.js

const ClassConfig = require('class-config-base')

For Web browser (only supporting es6)

<script src="class-config-base.min.js"></script>

Usage

Define default config object. This object determines the property default values, the property structure and the property data types of the class config class.
```
const defaultConfig = { top: 0, left: 0, right: 100, bottom: 50 }
```

Define the class config class.

defineMorePrivates method is optional and provides a timing to define more private data than private data defined by defaultConfig.
defineAccessors method is optional and creates descriptors to override property accessors.
defineInterfaces method creates descriptors to define properties and methods of the target interfacial class.

class RectangleConfig extends ClassConfig {
  constructor (initConfig, opts) {
    super(initConfig, defaultConfig, opts)
  }

  defineMorePrivates ($private) {
    $private.zoom = 1
    $private.zoomRange = { min: 0.2, max: 5 }
  }

  defineAccessors ($private, config) {
    return {
      zoom: { /* writable property */
        enumerable: true,
        get () { return $private.zoom },
        set (v) {
          v = Math.max(v, config.zoomRange.min)
          v = Math.min(v, config.zoomRange.max)
          $private.zoom = v
        },
      },
    }
  }
  
  get width () { return this.right - this.left }
  get height () { return this.bottom - this.top }

  defineInterfaces (config, instance) {
    return {
      width: { /* writable property */
        enumerable: true,
        get () { return config.width * config.zoom },
        set (v) { config.right = config.left + v / config.zoom },
      },
      height: { /* writable property */
        enumerable: true,
        get () { return config.height * config.zoom },
        set (v) { config.bottom = config.top + v / config.zoom },
      },
      area: { /* replaceable property */
        enumerable: true,
        configurable: true,
        set (value) { Object.defineProperty(instance, 'area', {
          enumerable: true,
          configuable: true,
          writable: true,
          value,
        }) },
        get () {
          return config.width * config.zoom * config.height * config.zoom
        },
      },
      inflate: { /* method property */
        enumerable: true,
        configurable: true,
        writable: true,
        value: (dw, dh) => {
          config.right += dw
          config.bottom += dh
        },
      },
    }
  }
}

This module provides some useful functions to define accessors/interfaces simply. By using these functions, the above example can be rewritten as follows:

const { readonly, writable, replaceable, method } = ClassConfig

class RectangleConfig extends ClassConfig {

  constructor (initConfig, opts) {
    super(initConfig, defaultConfig, opts)
  }

  defineMorePrivates ($private) {
    $private.zoom = 1
    $private.zoomRange = { min: 0.2, max: 5 }
  }

  defineAccessors ($private, config) {
    return {
      zoom: writable({
        get () { return $private.zoom },
        set (v) {
          v = Math.max(v, config.zoomRange.min)
          v = Math.min(v, config.zoomRange.max)
          $private.zoom = v
        },
      }),
    }
  }
  
  get width () { return this.right - this.left }
  get height () { return this.bottom - this.top }

  defineInterfaces (config, instance) {
    return {
      width: writable({
        get () { return config.width * config.zoom },
        set (v) { config.right = config.left + v / config.zoom },
      }),
      height: writable({
        get () { return config.height * config.zoom },
        set (v) { config.bottom = config.top + v / config.zoom },
      }),
      area: replaceable({
        get () {
          return config.width * config.zoom * config.height * config.zoom
        },
      }),
      inflate: method((dw, dh) => {
        config.right += dw
        config.bottom += dh
      }),
    }
  }
}

Define the interfacial class with the class config.

class Rectangle {
  constructor (config) {
    config.configure(this)
  }
}

The interfaces of interfacial class can be also defined by following way:

class RectangleConfig extends ClassConfig {
  constructor (initConfig, opts) { ... }
  defineMorePrivates ($private) { ... }
  defineAccessors ($private, config) { ... }
}

class Rectangle {
  constructor (config) {
    config.configure(this, {
      width: writable({
        get () { return config.width * config.zoom },
        set (v) { config.right = config.left + v / config.zoom },
      }),
      height: writable({
        get () { return config.height * config.zoom },
        set (v) { config.bottom = config.top + v / config.zoom },
      }),
      area: replaceable({
        get () {
          return config.width * config.zoom * config.height * config.zoom
        },
      }),
      inflate: method((dw, dh) => {
        config.right += dw
        config.bottom += dh
      }),
    })
  }
}

Instantiate and use the interfacial class.

const rectConfig = new RectangleConfig()
const rect = new Rectangle(rectConfig)

console.log(rect.toString()) // => [object Rectangle]
console.log(Object.prototype.toString.call(rect)) // => [object Rectangle]
console.log(rectConfig.toString())
// => RectangleConfig { top: 0, left: 0, right: 100, bottom: 50, zoom: 1, zoomRange: { min: 0.2, max: 5 } }

console.log(rect.width) // => 100
console.log(rect.height) // => 50
console.log(rect.area) // => 5000

rect.inflate(10, 20)
console.log(rectConfig.toString())
// => RectangleConfig { top: 0, left: 0, right: 110, bottom: 70, zoom: 1, zoomRange: { min: 0.2, max: 5 } }
console.log(rect.width) // => 110
console.log(rect.height) // => 70
console.log(rect.area) // => 7700

A property value, even if it is read-only or hidden, can be updated with the class config object.

rectConfig.zoom = 0
console.log(rectConfig.toString())
// => RectangleConfig { top: 0, left: 0, right: 110, bottom: 70, zoom: 0.2, zoomRange: { min: 0.2, max: 5 } }
console.log(rect.width) // => 22
console.log(rect.height) // => 14
console.log(rect.area) // => 308

rectConfig.right = 160
rectConfig.bottom = 120
console.log(rectConfig.toString())
// => RectangleConfig { top: 0, left: 0, right: 160, bottom: 120, zoom: 0.2, zoomRange: { min: 0.2, max: 5 } }
console.log(rect.width) // => 32
console.log(rect.height) // => 24
console.log(rect.area) // => 768

Manage a config object and interfacial object

A mapping between a config class instance and a interfacial class instance can be managed by ClassConfig.Manager object.

const { Manager } = ClassConfig

const manager = new Manager()  // Create a manager

manager.set(rectConfig, rect)  // Set a mapping

const aConfig = manager.getConfig(rect)  // Get the configure object
const aRect = manager.getObject(rectConfig)  // Get the interfacial object

manager.delete(aRect)  // Delete a mapping

Share private data with another config object

A config object can share its private data (config.$private) with another config object, as follows:

const config1 = new RectangleConfig({ top: 1, left: 2, right: 12, bottom: 21 })
const config2 = new RectangleConfig(config1, { sharePrivate: true })

console.log(config1.toString())
// => RectangleConfig { top: 1, left: 2, right: 12, bottom: 21, zoom: 1, zoomRange: { min: 0.2, max: 5 } }
console.log(config2.toString())
// => RectangleConfig { top: 1, left: 2, right: 12, bottom: 21, zoom: 1, zoomRange: { min: 0.2, max: 5 } }

config1.right = 102
console.log(config1.toString())
// => RectangleConfig { top: 1, left: 2, right: 102, bottom: 21, zoom: 1, zoomRange: { min: 0.2, max: 5 } }
console.log(config2.toString())
// => RectangleConfig { top: 1, left: 2, right: 102, bottom: 21, zoom: 1, zoomRange: { min: 0.2, max: 5 } }

API

class ClassConfig

Is a class to configure the target class instance from hiding place.

.constructor (initConfig, defaultConfig, opts) => ClassConfig

Is a constructor to creates an instance of this class. initConfig and defaultConfig are objects and can be nested objects. defaultConfig is to specify the default values and the types of the properties. So if a type of a property in initConfig is different from a type of a corresponding property in defaultConfig, the property value in initConfig is ignored.

Parameters:

Parameter	Type	Description
initConfig	object	A configuration object which has initial property values.
defaultConfig	object	A configuration object which has default property values.
opts	object	A option object (Optional)

Propeties of opts:

Property	Type	Description
sharePrivate	boolean	True, if sharing `.$private` of `initConfig` which is `ClassConfig` object. (By default, falsy)

Returns:

A ClassConfig object.

.configure (instance, descriptors) => Void

Configures the interfaces of the target class instance in its constructor.

Parameters:

Parameter	Type	Description
instance	object	A class instance to be configured.
descriptors	object	A plain object which has descriptors of interfaces of the target class instance.

.defineMorePrivates ($private) => Void

Defines more private data than private data defined in defaultConfig.

Parameters:

Parameter	Type	Description
$private	object	The root object to store private data of the config object.

.defineAccessors ($private, config) => object

Returns an object which maps between property key chains and property descriptors. A key chain is a string that concatenates all keys in a key path with dots. A descriptor is a thing used by Object.defineProperty.

This method is used to override accessors of the config class.

Parameters:

Parameter	Type	Description
$private	object	The root object to store private data of the config object.
config	`ClassConfig`	This config object.

Returns:

A nested plain object which contains property descriptors of accessors of this config object.

.defineInterfaces (config, instance) => Void

Returns an object which maps between property names and property descriptors. A descriptor is a thing used by Object.defineProperty.

This method defines the interfaces of the target class.

Parameters:

Parameter	Type	Description
config	`ClassConfig`	This config object.
instance	object	The instance of the interfacial class configured by this config object.

static .readonly ({ getter , enumerable }) => object

Returns a readonly property descriptor.

Parameters:

Parameter	Type	Description
getter	function	A getter for this property.
enumerable	boolean	A flag to show this property during enumeration of the properties.

Return:

A property descriptor of the target readonly property.

static .writable ({ getter, setter, , enumerable }) => object

Returns a writable property descriptor.

Parameter	Type	Descriptor
getter	function	A getter for this property.
setter	function	A setter for this property.
enumerable	boolean	A flag to show this property during enumeration of the properties.
configurable	boolean	A flag to change or delete this property.