CODEWITHSUNDEEP
javascriptinheritancecoffeescriptmixins
wizztjh
wizztjh

Reputation: 7041

How to merge instead of replace object when extend

class A
  constructor:
    //dosomething
  loadFunctions:
    loadDrillingCharges: (memoize) ->


class B extends A
  constructor:
    super()
  loadFunctions:
    loadLockDDR: (memoize) ->

(new B).loadFunctions will be an object with loadLockDDR attribute only

I want the (new B).loadFunctions to be { loadDrillingCharges: -> , loadLockDDR: -> }

I can _.extend(B::loadFunctions, A::loadFunctions) but it is not elegant.

I tried to use cocktail mixin but it screw up the super()

What can I do to merge the object after extend and not screw up the coffescript super.

Upvotes: 0

Views: 158

Answers (2)

Sylvain Leroux
Sylvain Leroux

Reputation: 52000

Not very sexy, but...

class A
  constructor: ->
    # dosomething
  loadFunctions: ->
    loadDrillingCharges: (memoize) ->


class B extends A
  constructor: ->
    super()
  loadFunctions: ->
    do (that=super()) ->
      that.loadLockDDR = (memoize) ->
      that

console.log (new A).loadFunctions()
console.log (new B).loadFunctions()

Producing:

{ loadDrillingCharges: [Function] }
{ loadDrillingCharges: [Function], loadLockDDR: [Function] }

Upvotes: 0

smilexu
smilexu

Reputation: 11

Mixins are not something supported natively by CoffeeScript, for the good reason that they can be trivially implemented yourself. For example, here’s two functions, extend() and include(), that’ll add class and instance properties respectively to a class: 

extend = (obj, mixin) ->
 obj[name] = method for name, method of mixin 
 obj

include = (klass, mixin) ->
 extend klass.prototype, mixin

# Usage
include Parrot,
 isDeceased: true

(new Parrot).isDeceased

Upvotes: 1

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