Make queries compatible with koa and yield keyword

[capaj]

According to this article it is not possible to use mongoose with yield keyword to get rid of callbacks. Could this be addressed in Mongoose 4.0.0?

[aheckmann]

Haven't tried it but I'm guessing that the following works:

yield Model.find(..).exec()

Can you confirm?

[bernhardw]

I can confirm that it works, at least for find() and create(). But it should work for all methods that return a promise as well.
@capaj You can check the API to see what methods return a promise.

[flockonus]

what about yield document.save() ?

Maybe I'm missing something, but to make it work i need to do:

var thunk = require('thunkify')
// ...
document.save = thunk(document.save)
document = yield document.save()

[bernhardw]

@flockonus save() doesn't return a promise yet, but it will in 3.10. See #1431

[bodokaiser]

The current most "native" workaround:

model.js

var thunkify = require('thunkify');

schema.method('persist', function() {
  return thunkify(this.save.bind(this));
});

routes.js

app.use(function *(next) {
  this.status = 200;

  yield model.persist()();
});

[paglias]

@bodokaiser did you get your code working? I get an error:Error: yield a function, promise, generator, array, or object

[paglias]

@bodokaiser no error but it looks like yield is never resolved

[bodokaiser]

@paglias yeah checkout #1812 (comment)

[paglias]

@bodokaiser thanks, actually I wasn't running next() in a middleware... sorry

[bodokaiser]

yeah generators are still somehow experimental. I also got some cases where I get undefined thrown as error and no idea where it comes from (though not from l´koa)

[paglias]

@bodokaiser it was my fault, totally :) Anyway I'm using

  schema.method('persist', thunkify(function(){
    return this.save.apply(this, arguments);
  }));

To avoid having to call it twice: persist() instead of persist()()

[bodokaiser]

If you use my plugin as linked than you also do not have to use it twice + no dependences + workable on all models :)

module.exports = function(schema) {
  schema.method('persist', function(body) {
    var model = this;

    return function(callback) {
      model.set(body)
      model.save(callback);
    }
  });
  schema.method('destroy', function() {
    var model = this;

    return function(callback) {
      model.remove(callback);
    }
  });
};

use with mongoose.use(require('./plugin'));

[iliakan]

@bodokaiser You have a typo in your last code.
mongoose.use(require('./plugin')); should be mongoose.plugin(require('./plugin'));

Thanks will try that.

[miickel]

model.create() returns a promise, so it is possible to use that as an alternative as well.

[neverfox]

Since thunks are on the way out of co, you can always promisify save with e.g. bluebird:

yield Promise.promisify(model.save, model)();