NodeJS Module Pattern - node.js

I'm about to begin writing a new module for a system I'm developing. We use a MySQL database (so I'm using node-mysql) which contains a customers table.
What I want to achieve is:
Outside of the module I'm looking to do var C = new Customer(1) where 1 is the customer ID.
Now when I want to get something from this customer, I can do C.email or C.first_name which will simply return a value.
I also need to be able to set values back on this customer, C.email = 'example#example.com' or perhaps:
C.set('email', 'example#example.com')
What would be the best pattern to create such a model?

I already have something like this... Not exactly what you demanded but very close to that
I have generalized the core part and here is the code..Hope this will help....
var mysql = require('mysql');
var con = mysql.createConnection({
host:"yourHostName",
user:"yourUserName",
password:"yourPassword"
});
con.query("use databaseName");
function getCustomerDetails(custId){
con.query("select * from customer where custId = "+custId,function(err,result,fields){
if(!err)
return result;
else
console.log(err);
});
}
function updateCustomerDetails(custId,fieldName,fieldValue){
con.query("update customer set "+fieldName+" = "+fieldValue+" where custId = "+custId,function(err,result,fields){
if(!err)
return true;
else
console.log(err);
return false;
});
}
exports.getCustomerDetails = getCustomerDetails;
exports.updateCustomerDetails = updateCustomerDetails;
And then suppose you saved the module as dbAccessModule.js Then you can use the functions like this
var C = require('./dbAccessModule');
result = C.getCustomerDetails(1);
console.log(result.fieldName);
var success = C.updateCustomerDetails(1,'name','sumit');
if(success)
console.log('Table Updated successfully....');
else
// take necessary action according to your application
One thing you need to take care of is that if you are updating any field with string value
then please don't forget to surround the value of fieldValue with single quotes.
If this is not what you asked for then please ignore it....

I recently created two database modules you might be interested in checking out to see if they fit your needs - an ORM: http://bookshelfjs.org and Query Builder: http://knexjs.org
The ORM is based off of the design patterns of Backbone.js
So, you'd be able to do something like this:
// Create the base customer object
var Customer = Bookshelf.Model.extend({
tableName: 'customers'
});
// Create a new customer instance with an id of 1, fetch it, and then
// act on the result model 'customer'.
new Customer({id: 1}).fetch().then(function(customer) {
console.log(customer.get('name'))
customer.set('email', 'email#example.com')
return customer.save();
});
You could also extend the base Customer class to enable a shortened syntax, similar to what you're looking for:
// Create the base customer object, with a static findOne method.
var Customer = Bookshelf.Model.extend({
tableName: 'customers'
}, {
find: function(id) {
return new this({id: id}).fetch();
}
});
Customer.find(1).then(function(C) {
console.log(C.get('name'))
C.set('email', 'email#example.com')
});

Related

How do I increment a value for an existing object in Firebase?

I'm building a step counter app.
I got an iOS app that pushes the sum of each day to /users/{mobile}/steps/{date}/
When a new steps child is updated or added, I want to sum the value of all the steps for that particular user and update his stepsTotal.
To achieve that I need to
Find the original user and sum all the steps.
Save the new value to stepsTotal.
I would be most grateful if someone could give some help here. :-)
database
{
"users": {
"92291000": {
"firstName": "Tore",
"stepsTotal": "1500",
"steps": {
"02-09-2017": "500",
"03-09-2017": "1000"
},
import.js
var db = admin.database();
var dbRoot = db.ref("/");
var usersRef = dbRoot.child("users");
// This works
function saveUser(attributes) {
let mobile = attributes.mobile;
delete attributes['mobile']
let user = usersRef.child(mobile);
user.update(attributes);
}
function increaseSteps( { mobile=null, steps=null } = {}) {
// Find the User
console.log("looking for mobile", mobile); // OK
let userRef = usersRef.child(mobile);
// Here I'm not able to read the old data from the user.
userRef.transaction(function(user) {
console.log("user: ", user); // null
// ^ User is null.
});
/*
If I mangage to find user above, I expect to do something like this.
Or it is possible to only update *stepsTotal*?
*/
let attributes = {
firstName: user.firstName,
lastName: user.lastName,
stepsTotal: user.stepsTotal + steps,
}
user.update( attributes );
}
If I understand correctly, you have a problem in this snippet of the code:
let userRef = usersRef.child(mobile);
// Here I'm not able to read the old data from the user.
userRef.transaction(function(user) {
console.log("user: ", user); // null
// ^ User is null.
});
In Firebase Database transactions the initial value is often null. From the Firebase documentation on transactions:
Transaction Function is Called Multiple Times
Your transaction handler is called multiple times and must be able to handle null data. Even if there is existing data in your database it may not be locally cached when the transaction function is run.
This is due to how Firebase transactions work behind the scenes. To learn more about that, see my answers here Transcation updateFunction parameter is null and Firebase runTransaction not working.
The solution is to handle both cases: if the user node doesn't exist yet count the initial number of steps, otherwise update the number of steps:
let userRef = usersRef.child(mobile);
userRef.transaction(function(user) {
return (user || 0) + new_steps_for_user;
});

Trying to create an instance and multiple related instances in a many to many relationship

I am attempting to create an instance and multiple related instances with a many to many relation using a junction table.
While creating the multiple related instances, I need to add a value to a property on the junction table as well. I don't know if it is my lack of knowledge of sequelize or promises that is causing my problem.
The code I am using is below. This code does add the items to the database, but I need to redirect after the operation has completed, which is not working.
Basically, I need to create a Recipe. Once that is created, I need to create Ingredients and relate them to that Recipe. The ingredients are stored in an array coming from a form on an HTML page. While relating the Ingredients, I need to add the ingredient_quantity to the RecipeIngredients table, which is the through part of the relationship (the junction table).
global.db.Recipe.belongsToMany(
global.db.Ingredient,
{
as: 'Ingredients',
through: global.db.RecipeIngredients,
foreignKey: 'recipe_id'
});
global.db.Ingredient.belongsToMany(
global.db.Recipe,
{
as: 'Recipes',
through: global.db.RecipeIngredients,
foreignKey: 'ingredient_id'
});
router.post('/new', ensureLoggedIn, bodyParser.json(), function (req, res) {
var recipeName = req.body.recipe_name;
var steps = req.body.steps;
var ingredients = req.body.ingredients;
var ingredientQty = {};
var currentIngredient;
var ingredientsToAdd = [];
db.Recipe.create({
recipe_name: recipeName,
directions: steps,
FamilyId: req.user.FamilyId,
CreatedBy: req.user._id
})
.then(function (recipe) {
for (var i = 0; i < ingredients.length; i++) {
currentIngredient = ingredients[i];
ingredientQty[currentIngredient.ingredient_name] =
currentIngredient.quantity;
db.Ingredient.findOrCreate({
where: {
ingredient_name: currentIngredient.ingredient_name,
FamilyId: req.user.FamilyId
}
})
.spread(function (ingredient, created) {
if (created) {
console.log("Added Ingredient to DB: " +
currentIngredient.ingredient_name);
}
ingredient.Recipes = {
ingredient_quantity:
ingredientQty[ingredient.ingredient_name]
};
ingredient.CreatedBy = req.user._id;
recipe.addIngredient(ingredient)
.then(function () {
console.log("Added Ingredient " + ingredient.ingredient_name
+ " to Recipe " + recipe.recipe_name);
});
})
}
})
.finally(function(recipe){
res.redirect('/recipes');
});
});
Any help would be greatly appreciated. I know that I am running into issues because of trying to use promises inside of a loop, I just don't know how else I can accomplish this.
Using sequelize, you can create objects along with its associated objects in one step, provided all objects that you're creating are new. This is also called nested creation. See this link and scroll down to section titled "Creating with associations"
Coming to your issue, you've a many-to-many relationship between Recipe and Ingredient, with RecipeIngredients being the join table.
Suppose you've a new Recipe object which you want to create, like:
var myRecipe = {
recipe_name: 'MyRecipe',
directions: 'Easy peasy',
FamilyId: 'someId',
CreatedBy: 'someUserId'
}
And an array of Ingredient objects, like:
var myRecipeIngredients = [
{ ingredient_name: 'ABC', FamilyId: 'someId'},
{ ingredient_name: 'DEF', FamilyId: 'someId'},
{ ingredient_name: 'GHI', FamilyId: 'someId'}]
// associate the 2 to create in 1 step
myRecipe.Ingredients = myRecipeIngredients;
Now, you can create myRecipe and its associated myRecipeIngredients in one step as shown below:
Recipe.create(myRecipe, {include: {model: Ingredient}})
.then(function(createdObjects){
res.json(createdObjects);
})
.catch(function(err){
next(err);
});
And that is all !!
Sequelize will create 1 row in Recipe, 3 rows in Ingredient and 3 rows in RecipeIngredients to associate them.
I was able to fix the problem that I was having. The answers here helped me come up with my solution.
I am posting the solution below in case anyone else runs into a similar issue. I created a variable to store the Promise from Recipe.create(), I used Promise.map to findOrCreate all of the ingredients from the form data. Because findOrCreate returns an array containing Promise and a boolean for if the item was created, I then had to get the actual ingredients out of the results of the Promise.map function. So I used the JavaScript array.map() function to get the first item from the arrays. And finally, use Promise.map again to add each Ingredient to the Recipe
var ingredients = req.body.ingredients,
recipeName = req.body.recipeName,
ingredientsQty = {}; // Used to map the ingredient and quantity for the
// relationship, because of the Junction Table
var recipe = models.Recipe.create({recipe_name: recipeName});
// Use Promise.map to findOrCreate all ingredients from the form data
Promise.map(ingredients, function(ing){
ingredientsQty[ing.ingredient_name] = ing.ingredient_quantity;
return models.Ingredient.findOrCreate({ where: { ingredient_name: ing.ingredient_name}});
})
// Use JavaScript's Array.prototype.map function to return the ingredient
// instance from the array returned by findOrCreate
.then(function(results){
return results.map(function(result){
return result[0];
});
})
// Return the promises for the new Recipe and Ingredients
.then(function(ingredientsInDB){
return Promise.all([recipe, ingredientsInDB]);
})
// Now I can use Promise.map again to create the relationship between the /
// Recipe and each Ingredient
.spread(function(addedRecipe, ingredientsToAdd){
recipe = addedRecipe;
return Promise.map(ingredientsToAdd, function(ingredientToAdd){
ingredientToAdd.RecipeIngredients = {
ingredient_quantity: ingredientsQty[ingredientToAdd.ingredient_name]
};
return recipe.addIngredient(ingredientToAdd);
});
})
// And here, everything is finished
.then(function(recipeWithIngredients){
res.end
});

Nested transactions with pg-promise

I am using NodeJS, PostgreSQL and the amazing pg-promise library. In my case, I want to execute three main queries:
Insert one tweet in the table 'tweets'.
In case there is hashtags in the tweet, insert them into another table 'hashtags'
Them link both tweet and hashtag in a third table 'hashtagmap' (many to many relational table)
Here is a sample of the request's body (JSON):
{
"id":"12344444",
"created_at":"1999-01-08 04:05:06 -8:00",
"userid":"#postman",
"tweet":"This is the first test from postman!",
"coordinates":"",
"favorite_count":"0",
"retweet_count":"2",
"hashtags":{
"0":{
"name":"test",
"relevancetraffic":"f",
"relevancedisaster":"f"
},
"1":{
"name":"postman",
"relevancetraffic":"f",
"relevancedisaster":"f"
},
"2":{
"name":"bestApp",
"relevancetraffic":"f",
"relevancedisaster":"f"
}
}
All the fields above should be included in the table "tweets" besides hashtags, that in turn should be included in the table "hashtags".
Here is the code I am using based on Nested transactions from pg-promise docs inside a NodeJS module. I guess I need nested transactions because I need to know both tweet_id and hashtag_id in order to link them in the hashtagmap table.
// Columns
var tweetCols = ['id','created_at','userid','tweet','coordinates','favorite_count','retweet_count'];
var hashtagCols = ['name','relevancetraffic','relevancedisaster'];
//pgp Column Sets
var cs_tweets = new pgp.helpers.ColumnSet(tweetCols, {table: 'tweets'});
var cs_hashtags = new pgp.helpers.ColumnSet(hashtagCols, {table:'hashtags'});
return{
// Transactions
add: body =>
rep.tx(t => {
return t.one(pgp.helpers.insert(body,cs_tweets)+" ON CONFLICT(id) DO UPDATE SET coordinates = "+body.coordinates+" RETURNING id")
.then(tweet => {
var queries = [];
for(var i = 0; i < body.hashtags.length; i++){
queries.push(
t.tx(t1 => {
return t1.one(pgp.helpers.insert(body.hashtags[i],cs_hashtags) + "ON CONFLICT(name) DO UPDATE SET fool ='f' RETURNING id")
.then(hash =>{
t1.tx(t2 =>{
return t2.none("INSERT INTO hashtagmap(tweetid,hashtagid) VALUES("+tweet.id+","+hash.id+") ON CONFLICT DO NOTHING");
});
});
}));
}
return t.batch(queries);
});
})
}
The problem is with this code I am being able to successfully insert the tweet but nothing happens then. I cannot insert the hashtags nor link the hashtag to the tweets.
Sorry but I am new to coding so I guess I didn't understood how to properly return from the transaction and how to perform this simple task. Hope you can help me.
Thank you in advance.
Jean
Improving on Jean Phelippe's own answer:
// Columns
var tweetCols = ['id', 'created_at', 'userid', 'tweet', 'coordinates', 'favorite_count', 'retweet_count'];
var hashtagCols = ['name', 'relevancetraffic', 'relevancedisaster'];
//pgp Column Sets
var cs_tweets = new pgp.helpers.ColumnSet(tweetCols, {table: 'tweets'});
var cs_hashtags = new pgp.helpers.ColumnSet(hashtagCols, {table: 'hashtags'});
return {
/* Tweets */
// Add a new tweet and update the corresponding hash tags
add: body =>
db.tx(t => {
return t.one(pgp.helpers.insert(body, cs_tweets) + ' ON CONFLICT(id) DO UPDATE SET coordinates = ' + body.coordinates + ' RETURNING id')
.then(tweet => {
var queries = Object.keys(body.hashtags).map((_, idx) => {
return t.one(pgp.helpers.insert(body.hashtags[i], cs_hashtags) + 'ON CONFLICT(name) DO UPDATE SET fool = $1 RETURNING id', 'f')
.then(hash => {
return t.none('INSERT INTO hashtagmap(tweetid, hashtagid) VALUES($1, $2) ON CONFLICT DO NOTHING', [+tweet.id, +hash.id]);
});
});
return t.batch(queries);
});
})
.then(data => {
// transaction was committed;
// data = [null, null,...] as per t.none('INSERT INTO hashtagmap...
})
.catch(error => {
// transaction rolled back
})
},
NOTES:
As per my notes earlier, you must chain all queries, or else you will end up with loose promises
Stay away from nested transactions, unless you understand exactly how they work in PostgreSQL (read this, and specifically the Limitations section).
Avoid manual query formatting, it is not safe, always rely on the library's query formatting.
Unless you are passing the result of transaction somewhere else, you should at least provide the .catch handler.
P.S. For the syntax like +tweet.id, it is the same as parseInt(tweet.id), just shorter, in case those are strings ;)
For those who will face similar problem, I will post the answer.
Firstly, my mistakes:
In the for loop : body.hashtag.length doesn't exist because I am dealing with an object (very basic mistake here). Changed to Object.keys(body.hashtags).length
Why using so many transactions? Following the answer by vitaly-t in: Interdependent Transactions with pg-promise I removed the extra transactions. It's not yet clear for me how you can open one transaction and use the result of one query into another in the same transaction.
Here is the final code:
// Columns
var tweetCols = ['id','created_at','userid','tweet','coordinates','favorite_count','retweet_count'];
var hashtagCols = ['name','relevancetraffic','relevancedisaster'];
//pgp Column Sets
var cs_tweets = new pgp.helpers.ColumnSet(tweetCols, {table: 'tweets'});
var cs_hashtags = new pgp.helpers.ColumnSet(hashtagCols, {table:'hashtags'});
return {
/* Tweets */
// Add a new tweet and update the corresponding hashtags
add: body =>
rep.tx(t => {
return t.one(pgp.helpers.insert(body,cs_tweets)+" ON CONFLICT(id) DO UPDATE SET coordinates = "+body.coordinates+" RETURNING id")
.then(tweet => {
var queries = [];
for(var i = 0; i < Object.keys(body.hashtags).length; i++){
queries.push(
t.one(pgp.helpers.insert(body.hashtags[i],cs_hashtags) + "ON CONFLICT(name) DO UPDATE SET fool ='f' RETURNING id")
.then(hash =>{
t.none("INSERT INTO hashtagmap(tweetid,hashtagid) VALUES("+tweet.id+","+hash.id+") ON CONFLICT DO NOTHING");
})
);
}
return t.batch(queries);
});
}),

mongoose, getting object's id after using collection.insert

I'm trying to get the object id after adding it to the db (using collection.insert)
mongoose.model('Persons').collection.insert(person, function(err, newPerson) {
console.log('lets see you', newPerson);
});
and from the console I'm getting only result: { ok: 1, n: 1 } in stand of the new obj, any ideas how can I rich to the new object ?
thanks!
You can use save() here
var Persons = mongoose.model('Persons');
var personJSON = {
..... // persons schema values you want to insert
};
var person = new Persons(personJSON);
var result = yield person.save();
result variable will contain all the fields you inserted along with _id

How to automatically generate custom id's in Mongoose?

I'd like to manage my own _id's through Mongoose/MongoDB - as the default ones are pretty long and consume bandwidth.
The difficulty is that I need to create them (say, by incrementing a counter), but I need to do this in a concurrent environment (Node.JS). Is there a simple example I could follow that creates a schema, with a custom _id and a static method (or anything better) that automatically generates the next unique _id, whenever a new document is created?
You could use Mongo's findAndModify() to generate sequential values. Below is an example of this:
// (assuming db is a reference to a MongoDB database)
var counters = db.collection('counters');
var query = {'name': 'counterName'};
var order = [['_id','asc']];
var inc = {$inc:{'next':1}};
var options = {new: true, upsert: true};
counters.findAndModify(query, order, inc, options, function(err, doc) {
if(err) {
callback(err);
return;
}
var id = doc.next;
callback(null, id);
});
Although generating sequential IDs looks pretty on applications keep in mind that there are some drawbacks to them (e.g. when you need to split your database geographically) which is why Mongo uses the long pseudo-random keys that it does.
As Chad briefly touched on, Mongo implements a uuid system for you, taking into account the timestamp, network address, and machine name, plus an autoincrementing 2 digit counter (in the event that multiple entries with the same timestamp occur). This schema is used to allow distributed databases (ie, running different database instances on different machines) while ensuring that each entry will still have a unique identifier (because the machine name section will be different).
Trying to role out your own schema would likely greatly limit the scalability that mongo provides.
This should work
import { randomString } from '#/helpers'
const taskSchema = new mongoose.Schema({
_id: {
type: String,
unique: true,
default: randomString
},
title: String,
...
})
Random string function
// helpers
export const randomString = (length?: number) => {
let result = ''
const characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'
const charactersLength = characters.length
const n = length || 15
for (let i = 0; i < n; i++) {
result += characters.charAt(Math.floor(Math.random() * charactersLength))
}
return result
}
Tested result
{ "_id": "EIa9W2J5mY2lMDY", ... }

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