Question

I want to include the factory pattern in my modules. I have a module ServiceFactory.js that looks like this:

exports.createService = function(serviceName, paramObj){
  return require('Services/'+serviceName).Service.new(paramObj);
};

This module should require other modules (Services) by their names and create an instance. The general Service.js lookes like this:

const Base = require('base').Base;

exports.Service = Base.extend({
    getName: function(){
        return this.name;
    },
    invoke: function(){
        //do something
    },
});

All other Services extend the base Service. I collect all Services in a subfolder “Services” in “lib”. When I now use the createService method of my factory I get an error like: “Module: ServiceFactory … has no authority to load Service/…”

Is there a way to grant ServiceFactory the authority to load my Services or is there another way to achieve my goal?

Answer 1

The Add-on SDK resolves all requirements when the add-on is packaged, it doesn’t happen at run-time. I guess that this is done mostly for performance reasons (modules can be loaded from several locations, searching these location when the extension is running can be slow) but there is a security aspect as well – even if a module is compromised (unintentionally runs code that it got from a web page), it still cannot load any additional modules, in particular not the chrome module. But the end result is: you cannot decide dynamically which modules you want to use, you can only load the modules that you explicitly require in your source code.

The work-around in your case would be adding a function that is never called but has all the necessary require() calls to make sure that the SDK resolves them:

function dummy()
{
  require("Services/ServiceFoo");
  require("Services/ServiceBar");
  ...
}

Having this function in ServiceFactor.js will make sure that the createService() function can require these modules.