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 little big, and too many features in it. We just need some of the features(methods) inside. So as a class developer can consider these functions to extract, as a kind of ability to the user.

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.

Note: The same name of the methods will be replaced via the ability. These old methods will be lost. So, you must confirm whether there are the same methods in your class before you apply the new ability.

# ability.coffee
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: ->

# We set the `addRef` method as the core methods.
# The Core methods are the ability MUST have.
# they're used to check the same ability whether the ability already added.
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, exclude: '@someClassMethod' #someClassMethod would not be added to the class
  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 which could call the old(original) method. 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(life cycle). So the event-able of AbstractObject should be:

eventable         = require 'events-ex/eventable'
eventableOptions  = require './eventable-options'

module.exports = (aClass, aOptions)->
  eventable aClass, eventableOptions(aOptions)

# eventable-options.coffee
module.exports = (aOptions)->
  aOptions = {} unless aOptions
  aOptions.methods = {} unless aOptions.methods
  extend aOptions.methods,
    # override methods: (btw: classMethods to override the class methods)
    setObjectState: (value, emitted = true)->
      self= @self
      @super.call(self, value)
      self.emit value, self if emitted
      return
  ...
  return aOptions
  # more detail on [AbstractObject/src/eventable-options.coffee](https://github.com/snowyu/abstract-object)

TODO: need to more explain: 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('./lib/eventable-options')

module.exports = AbstractObject

API

just one function:

var customAbility = require('custom-ability')

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

arguments

• abilityClass (function): the class will become to abilitiable.
• coreMethod (string|arrayOf string): optional must have coreMethod(s).
  • note: @ prefix means class/static method.
• 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.

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

• class: the class to be injected the ability.
• options (object): optional options
  • include(array|string): only these methods will be added to the class
    • note: @ prefix means class/static method.
  • exclude(array|string): these methods would not be added to the class
    • note: the coreMethod could not be excluded. It's always added to the class.
    • note: @ prefix means class/static method.
  • methods(object): injected/hooked methods to the class
    • key: the method name to hook.
    • value: the new method function, if original method is exists or not in replacedMethods:
      • use this.super() to call the original method.
      • this.self is the original this object.
  • classMethods (object): hooked class methods to the class, it's the same usage as the methods.
  • replacedMethods (array): the method name in the array will be replaced the original method directly.

Specification

V1.6.2

• fix: use replace instead inject method if there is no such method on the target

  const makeAbility = require('custom-ability')
  class Feature {
    $init() {
      const Super = this.super
      const that = this.self || this
      if (Super) {
        if (Super.apply(that, arguments) === 'ok') return
      }
      that._init.apply(that, arguments)
    }
    _init() {console.log('feature init')}
  }
  Feature.prototype.init = function() {this._init.apply(this, arguments)}
  const addFeatureTo = makeAbility(Feature)
  
  class My {
  }
  addFeatureTo(My)
  expect(My.prototype.init).toStrictEqual(Feature.prototype.init)

• fix(1.6.1): the injectMethods(AOP) starting with "$" was incorrectly replaced with the original method

  const makeAbility = require('custom-ability')
  class Feature {
    // inject to the init method on target class
    $init() {
      const Super = this.super
      const that = this.self || this
      if (Super) {
        if (Super.apply(that, arguments) === 'ok') return
      }
      that._init.apply(that, arguments)
    }
    _init() {console.log('feature init')}
  }
  Feature.prototype.init = function() {this._init.apply(this, arguments)}
  const addFeatureTo = makeAbility(Feature)
  
  class My {
    init(doInitFeature = true) {
      // the my init procedure
      console.log('my init')
      if (!doInitFeature) return 'ok'
    }
  }
  addFeatureTo(My)
  const obj = new My
  obj.init()
  // my init
  // feature init
  obj.init(false)
  // my init

V1.6.0

• broken change The methods in ES6 Class all are non-enumerable. So they have an ability to call super method too if the target has the same method.

const createAbility = require('custom-ability')
class MyFeature {
  static coreAbilityClassMethod(){};
  coreAbilityMethod(){};
  init(){
    const Super = this.super // the original init method
    const that = this.self || this // the instance
    if (Super) {
      Super.apply(that, arguments)
    }
    // do the init from MyFeature
    console.log('init from MyFeature')
  };
}

const addFeatureTo = createAbility(MyFeature, ['coreAbilityMethod', '@coreAbilityClassMethod']);

class MyClass {
  init(hi) {
    console.log('init from MyClass', hi)
  }
}
// inject the static and instance methods to the MyClass.
addFeatureTo(MyClass);
const instance = new MyClass;
instance.init('hello');

V1.5.0

• broken change the class method name conversation to: @ prefix means class/static method.
  • include/exclude
  • coreMethod

V1.4.x

• Inject additional ability to each parent classes When the some parent classes has additional ability, and mark it has been injected. note: the additional ability does not include the ability itself.
• The methods of ability itself will be injected to the farthest parent class if possible. The static methods of it will be inject to the current class, and mark it has been injected too.
• Known Issues:
  • the middle parent classes has no the static methods of ability.

customAbility = require 'custom-ability'

class Test
  one: ->
  @one: ->

testable = customAbility Test #convert the class to testable ability

class Root
  $abilities:
    Test: -> # additional ability to Test
      methods:
        additional:->
        two: ->
class Mid
  inherits Mid, Root
  $abilities:
    Test: -> # additional ability to Test
      methods:
        additional:-> Mid.__super__.additional.apply(@, arguments)
        three: ->
class A
  inherits A, Mid
  testable A # make the class A testable.

# A should have all static methods of Test
# Mid,Root should have no any methods of Test
for k, v of Test
  Mid.should.not.have.ownProperty k
  Root.should.not.have.ownProperty k
  A.should.have.ownProperty k
  v.should.be.equal A[k]


# A and Mid should have no any methods of Test
# the Root should have all methods of Test
for k, v of Test::
  A::should.not.have.ownProperty k
  Mid::should.not.have.ownProperty k
  Root::should.have.ownProperty k

# Root should have additional methods:
Root::should.have.ownProperty 'additional'
Root::should.have.ownProperty 'two'

Mid::should.have.ownProperty 'additional'
Mid::should.have.ownProperty 'three'

V1.3.3

• use the injectMethods(AOP) for the methods of non-enumerable and beginning with '$' in an ability to call super method if the target has the same method. you can exclude it with normal name if it's not a core method.

customAbility = require 'custom-ability'

class PropertyManagerAbility
  constructor: ->@initialize.call @, arguments[gOptPos]
  # the non-enumerable property and beginning with '$' will
  # be injected to `initialize` method
  defineProperty @::, '$initialize', ->
    options = arguments[gOptPos]
    options?={}
    that = @
    if @super and @self
      inherited = @super
      that = @self
      inherited.apply(that, arguments)
    that._initialize options if isFunction that._initialize
    that.defineProperties(options.attributes)
    that.assign(options)

module.exports = customAbility PropertyManagerAbility, 'assign'

V1.3.x

• add the replaceMethods option to custom ability function.

• <broken change>: additional abilities usage changed

  • separate ability options object.

• 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 function to return the ability options object.

The AbstractObject need to hook some methods to make the eventable ability work correctly.

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

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

module.exports = AbstractObject

the eventable-options.coffee file:

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

the AbstractObject's 'eventable' function:

eventable         = require 'events-ex/eventable'
eventableOptions  = require './eventable-options'

module.exports = (aClass, aOptions)->
  eventable aClass, eventableOptions(aOptions)

V1.2.x (deprecated)

• 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)