Splatted objects

[satyr]

We already got splatted arrays [a, b...]. Now how about extending it to objects?

coffee> o = un: 42; console.dir {0: 1, o...}
{ '0': 1, un: 42 }

The compilation of {0: 1, o...} would be something like:

__mix({0: 1}, o)

where __mix is defined as:

(target, source) ->
  target[k] = v for k, v of source
  target

[jashkenas]

I'm not a big fan of overloading ... even more than it already is. Splats are for lists of things...

[satyr]

This feature would be handy because copying an object's props over another is a very common operation.

Our source code is no different--we even have two different helper fuctions that can be replaced by this.

[sstephenson]

I really like this idea. Almost all of my libraries have some sort of merge helper.

[michaelficarra]

Like jashkenas, I believe this is too much responsibility for the ... operator. Also, determining and then memorizing the exact semantics of this particular merge would be a nightmare. -1 for now.

[satyr]

Splats are for lists of things...

An object is effectively a list of properties, for that matter.

[TrevorBurnham]

This doesn't make sense to me. As Jeremy said, this puts a pretty big burden on the splat operator. What's worse,

{x, y} = obj

is valid shorthand for x = obj.x and y = obj.x, but

{a: x, b, c...} = obj

would be...what? Here, a and b are references to keys on obj, and x is a reference to a variable, but what is c? It can't mean "merge obj.c into this object," because there is no object. So is it a syntax error, or is there something useful that it could indicate?

I'd be happy to have a nice syntax for object merges, but this isn't the way to do it.

[satyr]

{a: x, b, c...} = obj

A similar situation to [a..., b...] = arr (multiple splats), where we lack a defined behavior. We'd just throw syntax error in these cases.

[jashkenas]

It's not only that -- the extend method really belongs on Object.prototype. It would be a shame if CoffeeScript supported a convenient syntax for mixing an object into an object literal, but lacked a syntax for mixing an object into a preexisting object.

Closing as a duplicate -- this issue has been discussed plenty before.

[satyr]

Yet another issue that's closed too fast, eh?

but lacked a syntax for mixing an object into a preexisting object

That's coming as well, of course.

Closing as a "duplicate" -- this issue has been discussed plenty before

Please provide links. Duplicate of what exactly?

[jashkenas]

Sure thing. #218, #377, at least.

[satyr]

http://github.com/satyr/coffee-script/commit/e2208e20d0a4e86eafd9d658fb5ff545ba76d9c8