Factory + Inheritance

factory_plus_inheritance.js

'use strict';

class ImportDaoInterface {

    /**
        This methods contract is x, y, z
    */
    getOrders(dateRange, cb) {
        throw 'Extend Me!'
    }

}



class GrubhubImportDao extends ImportDaoInterface {

    getOrders(dateRange, cb) {
        process.nextTick(function(){
            cb(false, [])
        })
    }

}



function ImportDaoFactory(whichOne){
    //try {
    //    var importDao = new require('../dao/'+whichOne+'Dao')
    //} catch (e) {
    //    throw new Error('Not Implemented')
    //}
    // the above for production, but for this all-in-one test case:
    var importDao = new GrubhubImportDao

    // can do factory things here if want to, like:
    var getOrdersWrapper = importDao.getOrders
    importDao.getOrders = function(dateRange,cb){
        getOrdersWrapper(dateRange,function(err,orders){
            if (err) {
                console.log('report error to sentry, etc')
            }
            cb(err,orders)
        })
    }

    return importDao
}



// test...
ImportDaoFactory('GrubhubImport').getOrders('last 3 hours', function(err,orders){
    console.log('orders=',orders)
})

Thats really cool.

And can always add properties/attrs like:

function ImportDaoFactory(whichOne, props){
    try {
        var importDao = new (require('../dao/'+whichOne+'Dao')(props))
    } catch (e) {
        throw new Error('Not Implemented')
    }

But I am against that cuz imho the instantiator should not know init values of a DAO/Adapter/whatever. That should be controlled by configs (or a separate class). It conflates responsibilities. Consider example where we leverage factory to cache instances and/or responses (to account for read slave lag)

I like the inheritance pattern with the caveat of:

1. Dynamically loading classes based on a string at runtime

The second thing is that the ImportDaoFactory will be super repetitive. You should be able to abstract away what interface you define for the DAO and the autoloading of the class. I'll get a revised version of it in a sec

https://gist.github.com/dbercht/f6dc3f61254f0ce2cc5c27f5ff365a18