class-config-base

class-config-base

The base class of a configuration class for a interfacial class.

Install

npm i class-config-base --save

Usage

Load this module :

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

Define a configration class :

const defaultConfig = {
  a: 0,
  b: { c: '', d: false },
}

class MyClassConfig extends ClassConfigBase {
  constructor (initConfig) {
    super(initConfig, defaultConfig)
  }
}

let myConfig = new MyClassConfig()
console.log(myConfig) // => MyClassConfig { a: 0, b: { c: '', d: false } }

myConfig.a = 123
myConfig.b.c = 'ABC'
myConfig.b.d = true
console.log(myConfig) // => MyClassConfig { a: 123, b: { c: 'ABC', d: true } }

myConfig = new MyClassConfig({ a: 9, b: { c: 'Z', d: true } })
console.log(myConfig) // => MyClassConfig { a: 9, b: { c: 'Z', d: true } }

Define accessors of the configuration class

class MyClassConfig extends ClassConfigBase {
  constructor (initConfig) {
    super(initConfig, defaultConfig)
  }

  getAccessorDescriptors () {
    return {
      'a': parent => ({
        enumerable: true,
        get () { return parent.a },
        set (v) {},
      })

      'b.c': parent => ({
        get () { return parent.c },
        set (v) {
          if (parent.d) {
            parent.c = v
          }
        },
      }),
    }
  }
}

let myConfig = new MyConfig()
console.log(myConfig) // => MyClassConfig { a: 0, b: { c: '', d: false } }

myConfig.a = 123
myConfig.b.d = true
myConfig.b.c = 'ABC'
console.log(myConfig) // => MyClassConfig { a: 0, b: { c: 'ABC', d: true } }

myConfig.$private.a = 123  // `$private` property holds the entity
console.log(myConfig) // => MyClassConfig { a: 123, b: { c: 'ABC', d: true } }

Define a interfacial class which doesn't have property entities :

class MyClassConfig extends ClassConfigBase {
  constructor (initConfig) {
    super(initConfig, defaultConfig)
  }

  getAccessorDescriptors () {
    return {
      'a' : parent => ({
        get () { return parent.a },
        set (v) { parent.a = Math.max(0, v) }
      }),

      'b.c': parent => ({
        get () { return parent.c },
        set (v) {
          if (parent.d) {
            parent.c = v
          }
        },
      }),
    }
  }

  getInterfaceDescriptors () {
    const self = this

    return {
      myA: {
        enumerable: true,
        set (v) { self.a = v },
        get () { return self.a },
      },

      myC: {
        enumerable: true,
        set (v) { self.b.c = v },
        get () { return self.b.c },
      },

      myD: {
        enumerable: true,
        set (v) { self.b.d = v },
        get () { return self.b.d },
      },

      toString: {
        set (v) { this.toString = v },
        get () { return () => stringer(this) },
      },
    }
  }
}

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

let myConfig = new MyConfig({ a: 999, b: { c: 'AAA', d: true } })
let myObj = new MyClass(myConfig)

myObj.myA // => 999
myObj.myC // => 'AAA'
myObj.myD // => true
myObj.toString() // => MyClass { myA: 999, myB: 'AAA', myC: true }

API

constructor(initConfig, defaultConfig)

Constructs a configuration class instance. initConfig and defaultConfig is plain objects and may be nested objects. defaultConfig is to specify the default values and the type of the properties. So if a property of initConfig is different from a corresponding property of defaultConfig, the property value of initConfig is ignored.

Parameter:

• initConfig [object] : a configuration object which has initial property values.
• defaultConfig [object] : a configuration object which has default property values.

getAccessorDescriptors() => object

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

This method may override to configure accessors of the config class.

Return: [object]

An object which maps between property key chains and property descriptors of the config class instance.

The format of an entry in the returned object is as follows:

  getAccessorDescriptors () {
    return {
      /* An example of an entry in the returned object */
      'a.b.c' : function (parent, key, Info) {
        return {
          enumerable: true,
          configurable: false,
          get () { return parent[key] },
          set (v) { parent[key] = v },
        }
      },
      ...
    }
  }

The entry is a function of which the arguments are parent, key, info. parent is same with config.a.b, and key is same with 'c'. info is same with nodeInfo of each-props.

getInterfaceDescriptors() => object

Returns an object which maps between property name and property descriptors. A descriptor is the one used by Object.defineProperty.

This method may override to configure interfaces of the target class.

Returns: [object]

An object which maps between property name and property descriptors of the target class.

The format of an entry in the returned object is as follows:

  getInterfaceDescriptors () {
    const self = this
    
    return {
      /* An example of an entry in the returned object */
      'a' : {
        return {
          enumerable: true,
          configurable: false,
          get () { return self.a },
          set (v) { self.a = v },
        }
      },
      ...
    }
  }

configure(instance)

Configures the target class instance in its constructor.

Parameters:

• instance [object] : A class instance to be configured.

License

Copyright (C) 2017 Takayuki Sato

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