Meteor wrapAsync has no method 'apply' - asynchronous

Question

I'm trying to take an async function, wrap it and call it:
s3 = new AWS.S3();
Meteor.methods({
getbuckets: function( params, buckets ) {
var buckets = Meteor.wrapAsync(
s3.listBuckets( params, function( err, data ) {
if ( err ) {
console.log( err, err.stack ); // error
} else {
return buckets;
}
return {};
}) // End listBuckets
); // End wrapAsync
return buckets( params );
}
});
When calling the method, I'm getting this error:
TypeError: Object # has no method 'apply'
this is pointing to the line with buckets( params )

Answer 1

Meteor.wrapAsync takes an existing asynchronous method method, such as s3.listBuckets. The second parameter contains the context this should bind to. This should work:
Meteor.methods({
getbuckets: function(params) {
var listBuckets = Meteor.wrapAsync(s3.listBuckets, s3)
return listBuckets(params);
}
});

Answer 2

Meteor.wrapAsync takes a function as an argument. What you are doing, is executing the function s3.listBuckets and passing the return value as an argument to Meteor.wrapAsync. Which doesn't have the prototype Function. So what you need to do is wrap it in an anonymous function, like this:
Meteor.methods({
getbuckets: function( params, buckets ) {
var buckets = Meteor.wrapAsync(
function bucketLister (params, resolveFuture) {
s3.listBuckets( params, function( err, data ) {
if ( err ) {
console.log( err, err.stack ); // error
resolveFuture(false)
} else {
resolveFuture(buckets);
}
return {};
}) // End listBuckets
} // End bucketLister
); // End wrapAsync
return buckets( params );
}
});
The function passed to Meteor.wrapAsync takes a function resolveFuture as it's argument. We pass the actual return value to it. To learn more about this check the meteor source code or the fibers documentation on resolvers