class-config-base

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

1. 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 = { a: '', b: { c: 0, d: 1 } }
   

2. 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 MyClassConfig extends ClassConfig {
   
     constructor (initConfig) {
       super(initConfig, defaultConfig)
     }
   
     defineMorePrivates ($private) {
       $private.e = { f: [1, 2, 3] }
     }
   
     defineAccessors ($private, config) {
       return {
         'b.c': {
           enumerable: true,
           get () { return $private.b.c },
           set (v) { $private.b.c = Math.max(0, v) },
         }
       }
     }
   
     defineInterfaces (config, instance) {
       return {
         myA: { /* readonly property */
           enumerable: true,
           set () {},
           get () { return config.a },
         },
         myC: { /* writable property */
           enumerable: true,
           set (v) { config.b.c = v },
           get () { return config.b.c },
         },
         myF: { /* replaceable property */
           enumerable: true,
           configurable: true,
           set (value) { Object.defineProperty(instance, 'myF', {
             enumerable: true,
             configuable: true,
             writable: true,
             value,
           }) },
           get () { return config.e.f },
         },
         myG: { /* method property */
           enumerable: true,
           configurable: true,
           writable: true,
           value: (v) => { return config.b.d * v },
         },
       }
     }
   }
   

   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 MyClassConfig extends ClassConfig {
   
     constructor (initConfig) {
       super(initConfig, defaultConfig)
     }
   
     defineMorePrivates ($private) {
       $private.e = { f: [1, 2, 3] }
     }
   
     defineAccessors ($private, config) {
       return {
         'b.c': writable({
           get () { return $private.b.c },
           set (v) { $private.b.c = Math.max(0, v) },
         }),
       }
     }
   
     defineInterfaces (config, instance) {
       return {
         myA: readonly({ get: () => config.a }),
         myC: writable({
           set: v => { config.b.c = v },
           get: () => config.b.c,
         }),
         myF: replaceable({ get: () => config.e.f }),
         myG: method((v) => { return config.b.d * v }),
       }
     }
   }
   

3. Define the interfacial class with the class config.

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

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

   class MyClassConfig extends ClassConfig {
     constructor (initConfig) { ... }
     defineMorePrivates ($private) { ... }
     defineAccessors ($private, config) { ... }
   }
   
   class MyClass {
     constructor (config) {
       config.configure(this, {
   
         myA: readonly({ get: () => config.a }),
   
         myC: writable({
           set: v => { config.b.c = v },
           get: () => config.b.c,
         }),
   
         myF: replaceable({ get: () => config.e.f }),
   
         myG: method((v) => { return config.b.d * v }),
       })
     }
   }
   

4. Instantiate and use the interfacial class.

   const myCfg = new MyClassConfig({ a: 'Foo', b: { c: 123, d: true } })
   const myObj = new MyClass(myCfg)
   
   console.log(myObj.toString())  // [object MyClass]
   console.log(Object.prototype.toString.call(myObj)) // [object MyClass]
   console.log(myObj.myA) // 'Foo'
   console.log(myObj.myC) // 123
   console.log(myObj.myF) // [1, 2, 3]
   console.log(myObj.myG(2)) // 2
   
   myObj.myA = 'Bar'
   console.log(myObj.myA) // 'Foo'
   
   myObj.myC = 999
   console.log(myObj.myC) // 999
   
   myObj.myF = 123
   console.log(myObj.myF) // 123
   

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

   myCfg.a = 'Buz'
   myCfg.b.c = 666
   myCfg.b.d = 888
   
   console.log(myObj.myA) // 'Buz'
   console.log(myObj.myC) // 666
   console.log(myObj.myG(2)) // 1776
   

6. 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(myCfg, myObj)  // Set a mapping
   
   const aCfg = manager.getConfig(myObj)  // Get the configure object
   const aObj = manager.getObject(myCfg)  // Get the interfacial object
   
   manager.delete(aObj)  // Delete a mapping
   

API

class ClassConfig

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

.constructor (initConfig, defaultConfig) => ClassConfig

Is a constructor to creates an instance of this class. initConfig and defaultConfig are plain 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.

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 ] [, configurable ] }) => 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.

Return:

A property descriptor of the target writable property.

[static] .replaceable ({ getter [, enumerable ] }) => object

Returns a replaceable property descriptor.

Parameters:

Parameter	Type	Description
get	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 replaceable property.

[static] .method (fn) : object

Returns a property descriptor for a method.

Parameters:

Parameter	Type	Description
fn	function	A method function for this property.

Return:

A property descriptor of the target method property.

class ClassConfig.Manager

Is a manager class which has mappings of a config object and an object configured by it.

.constructor () => ClassConfig.Manager

Creates an instance of this class.

Returns:

A ClassConfig.Manager object.

.set (object, config) => Void

Sets a mapping of a config object and an object configured by it.

Parameters:

Parameter	Type	Description
object	object	The object configured by the config object.
config	ClassConfig	The config object.

.delete (objectOrConfig) => Void

Deletes a mapping of a config object and an object configured by it.

Parameters:

Parameter	Type	Description
objectOrConfig	object |ClassConfig	The object or config object to be deleted its mapping from this manager object.

.getConfig (object) => ClassConfig

Gets a config object corresponding to the specified object.

Parameters:

Parameter	Type	Description
object	object	The object registered with this manager object.

Returns:

The config object corresponding to the specified object.

.getObject (config) => object

Get an object corresponding to the specified config object.

Parameters:

Parameter	Type	Description
config	ClassConfig	The config object registered with this manager object.

Returns:

The object corresponding to the specified config object.

License

Copyright (C) 2017-2018 Takayuki Sato

This program is free software under MIT License. See the file LICENSE in this distribution for more details.