custom-ability

custom-ability

generate the ability which can be added to any class directly. It makes custom ability more easy.

Sometimes, we still feel that the class is a liitle big, and too many features in it. We just need some of the features inside. So as a class developer can consider these functions to extract, as a kind of ability to the user.

API

just one function:

var customAbility = require('custom-ability')

• customAbility(abilityClass[, coreMethod[, isGetClassFunction]])

arguments

• abilityClass (function): the class will become to ability able.
• coreMethod (string|array): optional must have coreMethod(s).
• isGetClassFunction (boolean): the AbilityClass is a function(aClass, aOptions) to return the real Ability Class if true. defaults to false.

return

• (function): a function which can inject the ability to any class directly.

the custom ability function has two arguments: function(class[, options])

• class: the class to be injected the ability.
• options (object): optional options
  • include (array|string): only these emitter methods will be added to the class
  • exclude (array|string): theses emitter methods would not be added to the class
    • note: the coreMethod could not be excluded. It's always added to the class.
  • methods (object): hooked methods to the class
    • key: the method name to hook.
    • value: the new method function
      • use this.super() to call the original method.
      • this.self is the original this object.
  • classMethods (object): hooked class methods to the class

Specification

V1.2.x

• Put the 'ability.js' file in your NPM Package folder which means this can be as ability. So you can use this way to get the ability:

ability  = require('custom-ability/require')

class MyClass
  #get the stateable ability from AbstractObject for MyClass
  ability 'abstract-object', MyClass

• Put the '$abilities'(object) property on your prototype of class if need to modify the class before apply ability.
  • the $abilities object key is the AbilityClass Name
  • the value is the modified ability function

AbstractObject = require('./lib/abstract-object')

AbstractObject.$abilities = {
  # "Eventable" is the AbilityClass name
  # the value is modified ability function.
  Eventable: require('./eventable')
}

module.exports = AbstractObject

the AbstractObject's 'eventable' function:

eventable         = require 'events-ex/eventable'

module.exports = (aClass)->
  eventable aClass, methods:
    # override methods:
    # we need to emit event when object state changes.
    setObjectState: (value, emitted = true)->
      self= @self
      @super.call(self, value)
      self.emit value, self if emitted
      return
    ...
# more detail on [AbstractObject/src/eventable](https://github.com/snowyu/abstract-object)

Usage

suppose we wanna add the RefCount ability to any class directly.

the RefCount ability will add the following members to your class. and you should implement the destroy method which will be called by release/free.

• properties:
  • RefCount (integer): the reference count.
• methods:
  • release()/free(): Decrements reference count for this instance. If it is becoming less than 0, the object would be (self) destroyed.
  • addRef(): Increments the reference count for this instance and returns the new reference count.

customAbility = require 'custom-ability'

class RefCountable
  # define the instance methods here:
  release: ->
      result = --@RefCount
      @destroy() unless result >= 0
      result
  free: @::release
  addRef: ->
    if not isUndefined @RefCount
      ++@RefCount
    else
      @RefCount = 1

  # the class methods if any:
  @someClassMethod: ->


module.exports = customAbility RefCountable, 'addRef'

do not forget to add the "ability" keyword to your package.json which means the ability power with it.

// package.json
"keywords": [
  "ability",
  ...
],

do not forget to add the "ability.js" file on your package root folder too.

now user use this ability like this:

refable = require 'ref-object/ability'

class MyClass
  refable MyClass
  destroy: ->console.log 'destroy'


my = new MyClass

my.addRef()
my.free() # nothing
my.free() # print the 'destroy' here.

More complicated example, you can see the events-ex/src/eventable.coffee.

additional $abilities

In order to make certain ability to work, you need to modify some methods of the class. this time we need the "additional abilities" now. eg, the event-able ability to AbstractObject. We need to send a notification event when the state of the object changes. So the event-able of AbstractObject should be:

eventable         = require 'events-ex/eventable'

module.exports = (aClass)->
  eventable aClass, methods:
    # override methods:
    setObjectState: (value, emitted = true)->
      self= @self
      @super.call(self, value)
      self.emit value, self if emitted
      return
# more detail on [AbstractObject/src/eventable](https://github.com/snowyu/abstract-object)

the original eventable('events-ex/eventable') is no useful for AbstractObject.

but we wanna the original eventable('events-ex/eventable') knows the changes and use it automatically.

eventable         = require 'events-ex/eventable'

class MyClass
  inherits MyClass, AbstractObject
  eventable MyClass

you just do this on the AbstractObject:

AbstractObject = require('./lib/abstract-object')

AbstractObject.$abilities =
  # "Eventable" is the AbilityClass name
  Eventable: require('./eventable')

module.exports = AbstractObject