Can't pass a closure to db.query

[espringe]

Example:

function f(what) {
  function map(doc) {
      if (doc.type === what)
          emit(doc._id, doc);
  }

  Database.query(map, function(){});
}

f('account')

Gives: Uncaught ReferenceError: what is not defined

[calvinmetcalf]

yes this is a known error, there is no way to get emit to be in scope without destroying the closure, though that gives me an idea

[espringe]

FWIW this works:

new Function('doc',
  'if (doc.type === ' + JSON.stringify(what) + ')' +
     'emit(doc._id, doc);'
);

But it makes me cry a little bit

[espringe]

there is no way to get emit to be in scope without destroying the closure

Does emit really need to be in scope? I'd prefer taking the emitter as an argument to the function .. or if that's too verbose, even using this.emit() ... as it's a lot less magical (And you don't need to smash the closure)

[calvinmetcalf]

I'm literally working on a pull to map reduce that takes emit as the second
argument

On Wed, Jan 29, 2014 at 2:15 PM, Eric Springer notifications@github.comwrote:

there is no way to get emit to be in scope without destroying the closure

Does emit really need to be in scope? I'd prefer taking the emitter as an
argument to the function .. or if that's too verbose, even using
this.emit() ... as it's a lot less magical (And you don't need to smash
the closure)

Reply to this email directly or view it on GitHubhttps://github.com/daleharvey/pouchdb/issues/1264#issuecomment-33619135
.

-Calvin W. Metcalf

[chesles]

Only problem with that is it breaks compatibility with couchdb, so you can't use the same map function as you do in couch (e.g. in a design doc) because emit is in scope in couch, but having an argument named emit would shadow that. It's an unfortunate situation, to be sure.

[calvinmetcalf]

@chesles this only applies to the temp views, not the design doc views, as they are stringified anyway so they have to be evaled

[chesles]

Ah, nice. That's awesome. +1 :)

[calvinmetcalf]

fyi I do have a pull for couchdb to get this syntax in apache/couchdb#127

[nolanlawson]

The new feature is merged in pouchdb/mapreduce. If you can't wait for the next release and want to try the bleeding edge, I've built it here: pouchdb-nightly.js and pouchdb-nightly.min.js.

var pouch = new PouchDB('mydb');
pouch.post({foo:'bar'})
.then(function(){
  var myFoo = 'bar';
  return pouch.query(function(doc, emit){
    if (doc.foo === myFoo){
      emit('it works!');
    }
  });
})
.then(function(result){
    console.log(result.rows[0].key); // 'it works!'
});

Oh yeah, did I mention the next version of Pouch will have promises?! @calvinmetcalf has been tearing it up recently.

[nolanlawson]

Documentation here btw.

[wspringer]

Awesome. By the way, my angular-pouchdb wrapper uses Angular's $q promise, if anyone is interested.