CoffeeScript - pass an anonymous function with parameters

Question

I can't fugure out how to pass an anonymous function that takes a parameter. Here is my situation:

class MyClass
  constructor: (@a) ->
    console.log("MyClass: created " + @a)

  show: ->
    console.log("MyClass: show " + @a)

then, with UnderscoreJS, this works:

_.map listOfMyClassObjects, (obj) -> obj.show

but I want to wrap the call to map in a separate function for convinience:

allMyClass(fun) ->
  _.map listOfMyClassObjects, fun(obj)

so that later I can do:

allMyClass((obj) -> obj.show())

but the browser console says:

Uncaught ReferenceError: fun is not defined
  (anonymous function)
  require../browser.CoffeeScript.run
  ...

What is the correct synthax? Also, is it possible to simplify like this?

 allMyClass(fun) ->
    _.map listOfMyClassObjects, obj[fun]()

 allMyClass(show())

UPDATE:

As per Thilo's answer, there was the syntax mistake in the function call. But also, there was a mistake in calling the function on the map iteration result. The working version is this:

allMyClass = (fun) ->
  _.map listOfMyClassObjects, (obj) -> fun(obj)

Still wandering if there is a shorter version of passing the class method to the allMyClass function though.

UPDATE2:

Simplification is possible like this:

allMyClass = (fun) ->
  _.map listOfMyclassObjects, (obj) -> obj[fun]()

allMyClass("show")

Passing arguments to the fun would require passing more arguments all in all.

In CoffeeScript the class body itself is a function expression that gets executed and returns the actual class constructor. So foo = 1 sets a variable within the scope of the Class body function expression itself. While foo: 1 sets a foo property with a value of 1 on the class prototype. — KGZM
– KGZM, Commented Jul 22, 2012 at 18:19

Thilo · Accepted Answer · 2012-07-22 10:14:05Z

2

Did you mean to define a function

allMyClass = (fun) ->
   _.map listOfMyClassObjects, fun(obj)

or method

allMyClass : (fun) ->
   _.map listOfMyClassObjects, fun(obj)

Without the = or : you were just calling allMyClass.

answered Jul 22, 2012 at 10:14

Thilo

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2 Comments

noncom Over a year ago

Oh! Just can't get used to CoffeeScript function notation ))) That's it! However, there was one more issue with my code, which I have depicted in the update.

Thilo Over a year ago

For any kind of syntax error, paste the offending lines into "Try CoffeeScript" and see what the JS looks like. jashkenas.github.com/coffee-script

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