piping

[icambron]

One thing that frustrates me about the gobble API is that I can't figure out how to compose things. Specifically, I want to do something like this:

var foo = function(node){
  return node.transform('stuff').transform('more-stuff');
}

gobble('src').pipe(foo).moveTo('place');
gobble('otherSrc').pipe(foo).moveTo('otherPlace');

I think pipe is probably a very simple function on Node that looks something like:

pipe(f){
  return f(this);
}

So...is there:

a) a way I'm missing to accomplish this? b) a way of hacking this in from userspace (I couldn't figure out how to monkey patch it)? c) a chance you'd take that addition as a PR?

[martypdx]

You can pass a function to .transform, isn't that the same thing?

[icambron]

Hmm, but the function passed to transform takes input and output dirs or files, not nodes. It's not obvious to me how to do this sort of thing with transform directly.

[martypdx]

File transformers take input, options where input is string contents of file and you return output:

gobble( 'src' ).transform( code => '/* bird */' + code ).moveTo( 'place' );

[icambron]

Right, but I want compose existing transformations and reuse those compositions. I don't need to work directly with the strings.

[msegado]

This is actually a common enough operation that there's been talk of adding a pipe operator into JS itself: https://github.com/mindeavor/es-pipeline-operator . That's a long way off though, so for now I could see the value of a pipe method for convenience. Biggest downside I see is that it increases the API surface area slightly.

Re. monkey patching, I think you can grab any Node instance and add the pipe method to the original prototype as follows (assuming the prototype chain is only one level deep; some experimentation may be needed):

nodeInstance.constructor.prototype.pipe = function pipe(f) { return f(this); };

[icambron]

Yeah, I played around with that for a bit yesterday and was surprised that I couldn't quite get anything to work. But could easily have been user error.

[msegado]

Odd. Give this a shot:

gobble('').constructor.prototype.pipe = function pipe(f) { return f(this); };

[EDIT: huh yeah, I see what you mean; not working for me]

[msegado]

OK... the Source and Merger nodes returned by gobble() are subclasses of Node, so we do need to go a level higher in the prototype chain. The following works, albeit with reliance on __proto__:

gobble([]).__proto__.__proto__.pipe = function pipe(f) { return f(this); };

[icambron]

Ah, right, I should have figured that out. Thanks!

[msegado]

Np! On Nov 27, 2015 5:38 PM, "Isaac Cambron" notifications@github.com wrote:

Ah, right, I should have figured that out. Thanks!

— Reply to this email directly or view it on GitHub https://github.com/gobblejs/gobble/issues/94#issuecomment-160223181.