Developing Microservices With Node.js by David Gonzalez

Author:David Gonzalez [Gonzalez, David]
Language: eng
Format: epub
ISBN: 9781785887406
Amazon: 1785887408
Publisher: Packt Publishing - ebooks Account
Published: 2016-05-04T18:30:00+00:00

Don't try to execute it, it is just a hypothetical example, but what we are doing in there is chain promises; and that makes the code vertical instead of ending up in a pyramid-shaped program, which is a lot harder to read, as shown in the following diagram:

Seneca, by default, is not a promise-oriented framework, but (there is always a but) using Bluebird, one of the most famous promises libraries in JavaScript, we can promisify Seneca, as follows:

var Promise = require('bluebird'); var seneca = require('seneca')(); // Promisify the .act() method; to learn more about this technique see: // http://bluebirdjs.com/docs/features.html#promisification-on-steroids var act = Promise.promisify(seneca.act, seneca); // Return no error and a success message to illustrate a resolved promise seneca.add({cmd: 'resolve'}, function (args, done) { done(null, {message: "Yay, I've been resolved!"}); }); // Return an error to force a rejected promise seneca.add({cmd: 'reject'}, function (args, done) { done(new Error("D'oh! I've been rejected.")); }); // Use the new promisified act() with no callback act({cmd: 'resolve'}) .then(function (result) { // result will be {message: "Yay, I've been resolved!"} since // its guaranteed to resolve }) .catch(function (err) { // Catch any error as usual if it was rejected }); act({cmd: 'reject'}) .then(function (result) { // Never reaches here since we throw an error on purpose }) .catch(function (err) { // err will be set with message "D'oh! I've been rejected." });

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