Can't Apply Lodash Partial To Function Created With Bluebird Promisifyall

The below code takes a all the methods in object lib and promisify's them. Then I can use the callback style function as a promise, which works. Then I use _.partial provide the fu

Solution 1:

Copying answer from the issue tracker:

The problem is _.partial does not maintain the this value which is required when you promisifyAll. You can either use promisify instead or you can use _.bind which is the appropriate lodash method.

var o = {};
o.dummy = function(path, encoding, cb){
  returncb(null, "file content here " + path + " " +encoding);
}

Promise.promisifyAll(o);

o.dummyAsync("a","b").then(function(data){
   console.log("HI", data); 
});

// and not `_.partial`var part = _.bind(o.dummyAsync, o, "a1", "b2");
part().then(function(data){
   console.log("Hi2", data); 
});

http://jsfiddle.net/hczmb2kx/

Solution 2:

promisifyAll does create methods that expect to be called on the original instance (as it does invoke the original .dummy method), but partial does not bind the functions you pass in, so you are getting a this error. You can use either readFile.call(lib) or _.partial(lib.dummyAsync.bind(lib), …) or just lib.dummyAsync.bind(lib, …).