destructuring parameters currently undocumented

[timoxley]

The destructuring parameter lists syntax isn't mentioned in the docs anywhere, and the syntax is really neat:

class Man
    constructor: ({@name, @description}) ->
        # empty constructor. is magic.
        # note the curly braces

# note the use of a named parameter list on initialisation    
dave = new Man
    name: 'Dave'
    description: 'a dude'

console.log "#{dave.name} is #{dave.description}" # output: Dave is a dude

Recommend adding to documentation.

[devongovett]

whoa nice. never knew about this, looks quite useful! :P

[nddrylliog]

Reminds me of ooc :D

Man: class {
    init: func (=name, =description)
}

Feels good ^^.

[erisdev]

Huh, I thoought this was documented because I knew about it. I wonder how I figured it out.

[codelahoma]

@erisdiscord Probably because it's shown in the Class example.

[timoxley]

@codelahoma is it? where?

[codelahoma]

Note I said shown, not documented. :-)

The Animal class here has a bodyless constructor: http://coffeescript.org/#classes

[timoxley]

@codelahoma that's different, this issue is about passing named params to constructor. read closely.

[codelahoma]

@secoif Gotcha (that IS neat). Sorry about the noise.

[codelahoma]

It actually works for functions in general, not just constructors.

fn = ({a,b}) ->
  console.log "a is #{a}, b is #{b}"

fn
 b: 5
 a: 1

compiles to

var fn;

fn = function(_arg) {
  var a, b;
  a = _arg.a, b = _arg.b;
  return console.log("a is " + a + ", b is " + b);
};

fn({
  b: 5,
  a: 1
});

@jashkenas Would it be better to document this in the Destructuring Assignment section, or in the Function Literals section with a link to the DA section?

[jashkenas]

Honestly, I forgot that we supported that ... and I'm not a huge fan of it, because it seems to make your function's API a bit less documented than writing it out more clearly:

fn = (options) ->
  {a, b} = options

... so that's probably the original reason why it's not documented.

[codelahoma]

Is this whole issue a non-starter, then?

Or is it just the plain function application you don't like, and the constructor usage should be documented?

[jashkenas]

I don't know. If we do document it, we should find a good real-world example where it really helps make the code more readable.

[michaelficarra]

@jashkenas: It eliminates a temporary variable. Any example of its usage would be a good example. I don't see why you don't like the feature. You say the function's API looks less documented, but it's definitely more clear to me when the possible keys for an options argument are listed right in the parameter list.