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Firebase query delete specific value from database

I have this data on my firebase:
transportation: {
"car" : {
"bus" : {
"toyota" : false,
"bmw" : true
},
"suv" : {
"honda" : false,
"toyota" : true,
}
}
}
I want to delete all child that have "false" value data so that my data looks like this:
transportation: {
"car" : {
"bus" : {
"bmw" : true
},
"suv" : {
"toyota" : true,
}
}
}

This is code,
var ref = firebase.database().ref().child('transportation/')
ref.once("value")
.then(function(snapshot) {
data = snapshot.val();
for (var i=0;i < Object.keys(data).length;i++){
Object.keys(data)[i].forEach(function(childSnapshot) {
if(childSnapshot.val() == "false"){
childSnapshot.ref.remove();
}
});
}
}).catch(function(error) {alert("Data could not be deleted." + error);}););

In order to delete record from fairbase with its value, bellow may work:
var dB = firebase.database()
dB.ref('transportation/car').once('value', snap={
snap.forEach(s =>{
var obj =s.val();
var keys = s.key;
for (var key in obj ) {
if (!obj[key]) {
// In order to delete: set the path null
dB.ref('transportation/car/' + keys + "/" + key).set(null);
}
}
});
});

To delete data with specific value which false in your case . We needs to fetch all data for a node and then map through the data using keys to delete the data with exact value of object with value false.
let transportationRef = firebase.database().ref().child('transportation/')
transportationRef.child("car").once('value', s => {
if (s.exists()) {
// map through objects returned from transportationRef and map through the objects
Object.keys(s.val()).map(k => {
// deleting the node which contains `false` as value
if(s.val()[k]=="false"){
s.ref.remove()
}
})
}
})

Meteor publication's this.ready doesn't trigger

I combined two of my publications into a single one, as they were very similar. Both of them returned a set of cursor. I've rewritten them in low-level API, in order to make some control on data removing.
My problem is that, for a reason I totally ignore, the subscription onReady callback is never triggered. I've got other low-level pubsub in my app which publish data in a similar way and that works perfectly.
On the server, all my logs are correctly displayed, and no error is shown. The publication is runned correctly and the data are effectively sent to the client.
On the client, none of the onReady or onError callback is triggered.
Publication :
Meteor.publish("getTalkthread", function ( thread_id ) {
unblock(this);
console.log("start");
let uids = tags = corrections = [],
self = this;
let posts_cursor = Modules.both.queryGet({
type : 'posts',
method : 'find',
query : { $or: [
{ _id: thread_id },
{ parent: thread_id }
]
},
projection : { sort : { _id: 1 },
limit : 50
}
});
let posts_array = posts_cursor.fetch(),
posts_ids = posts_array.map( e => ( e._id ) );
//console.log("fetched posts", posts_array);
let corrs_cursor = Modules.both.queryGet({
type : 'corrections',
method : 'find',
query : { talkId: { $in: posts_ids } },
projection : { sort : { _id: 1 },
limit : 50
}
});
let corrs_array = corrs_cursor.fetch();
//console.log("fetched corrs", corrs_array);
let posts_authors = posts_array.map( e => ( e.owner ) ),
corrs_authors = corrs_array.map( e => ( e.owner ) );
let users_ids = _.union( posts_authors, corrs_authors );
let users_cursor = Modules.both.queryGet({
type : 'users',
method : 'find',
query : { _id: { $in: users_ids } },
projection : { sort : { date: -1 },
limit : 100,
fields : USER_PROFILE_FIELDS_
}
});
//console.log("fetched users", users_cursor.fetch());
let observers = {};
observers.posts = posts_cursor.observeChanges({
added : ( id, fields ) => { console.log("post added " + id); self.added ("posts", id, fields); },
changed : ( id, fields ) => { console.log("post changed " + id); self.changed("posts", id, fields); },
removed : ( id ) => {
console.log("test");
if ( id != thread_id ) {
console.log(true);
self.removed("posts removed " + id);
}
}
});
observers.users = users_cursor.observeChanges({
added : ( id, fields ) => { console.log("user added " + id); self.added ("users", id, fields); },
changed : ( id, fields ) => { console.log("user changed " + id); },
removed : ( id ) => { console.log("user removed " + id); }
});
observers.corrs = corrs_cursor.observeChanges({
added : ( id, fields ) => { console.log("corr added " + id); self.added ("corrections", id, fields); },
changed : ( id, fields ) => { console.log("corr changed " + id); self.changed("corrections", id, fields); },
removed : ( id ) => { console.log("corr removed " + id); self.removed("corrections", id); }
});
console.log("observers created");
this.ready();
self.onStop( () => {
observers.posts.stop();
observers.users.stop();
observers.corrs.stop();
});
console.log("end");
});
Subscription :
console.log("sub");
self.subscribe("getTalkthread", id, self.rerun.get()), {
onReady: function () {
console.log("READY");
if ( !Posts.findOne({ _id: id } )) {
$("#404NotFound").show();
$("#isoContent").hide();
} else if ( Posts.findOne( id ) ) {
$("#isoContent").show();
}
$("#spin").hide();
},
onError: function () {
console.log("ERROR");
$("#spin").hide();
$("#404NotFound").show();
$("#isoContent").hide();
}
};
The client page is correctly rendered, but the DOM manipulation are not triggered, forbidding the display of the content. Does anyone see what I'm doing wrong here ?
Thanks you
EDIT:
I tried to return an array of the three cursors, and, for whatever reason, the problem is the same. However, I don't see why.

Though I don't understand why, using Arunoda's SubsManager instead of the native Meteor.subscribe resolved the problem.

Firebase Rule for Data Validation

Assuming a data structure like below, I want a rule that disallows adding new car makes, for example users cannot add "toyota". So, I need to .validate such that the .update must match an existing make.
I have tried using $cars with ".validate": "newData.val().contains($cars)" and all kind of other ways with no luck. Any help is appreciated.
My code is:
function setModel(model,make,key){
if (model && make && key){
var carsRef = ref.child('cars');
var makeRef = carsRef.child(make);
var modelRef = makeRef.child(model);
var obj = {};
obj[key] = true;
modelRef.update(obj, onComplete);
}
}
The firebase looks like:
{
"cars" : {
"chevrolet" : {
"silverado" : {
"id192874623" : true,
"id786766663" : true
}
},
"ford" : {
"taurus" : {
"id736273627" : true
}
},
"honda" : {
"accord" : {
"id635263535" : true
}
}
}}

To disallow adding new car brands:
"cars": {
"$brand": {
".validate": "data.exists()"
}
}
This is covered in the section on existing data vs new data of the documentation.

how to nest mongodb queries through node.js?

I am having a collection of users of the type -
{
"_id" : ObjectId("56f60e4eea8af4670408483e"),
"twitterHandle" : "shrutip",
"firstName" : "Shruti",
"lastName" : "Patil",
"emailID" : "shrutip#gmail.com",
"password" : "91382451347786e9b8f2f3817b27a2adfec1880c",
"phoneNumber" : "98739458789",
"location" : "San Jose",
"birthYear" : 1992,
"birthMonth" : 1,
"birthDay" : 10,
"followers" : [
"abhayp",
"anupd",
"lubdhal",
"poojag",
"prashantb",
"pratiksanglikar",
"shaileshyedge",
"shrutip"
],
"following" : [
"abhinavk",
"anupd",
"hiteshn",
"lubdhal",
"omkarn",
"poojag",
"pratiksanglikar",
"shaileshyedge",
"shrutip"
],
"tweets" : [
{
"tweet_id" : "3c50e98cf0c2298f40f98a013cd4a18a1443b7ac",
"tweet_text" : "At BJP youth wing meet, seniors worry over #JNU controversy, and not #RamTemple.",
"createdOn" : ISODate("2016-03-07T23:37:27Z"),
"tags" : [
"JNU",
"RamTemple"
]
}
]
}
I want to create feed (all tweets of the users the given user is following in ascending order of date) for any given user. I got the list of users which the given user is following, but I need to find the tweets of the found users. How do I do it in node.js? How to nest these queries?
What I've done so far is listed below -
var cursor = MongoDB.collection("users").find({
"twitterHandle": twitterHandle
});
cursor.each(function(err, doc) {
assert.equal(err, null);
if (doc != null) {
var followingCursor = MongoDB.collection("users").find( { twitterHandle: { $in: doc.following } } );
followingCursor.each(function (err, following) {
if(following != null) {
feed.push(following.tweets);
}
});
promise.resolve(feed);
}
});
But somehow, the promise gets resolved before the second query executes.
How do I ensure that all the iterations of followingCursor.each are executed before I return the promise?

Eventually I found out the answer myself.
if (doc != null) {
var followingCursor = MongoDB.collection("users").find( { twitterHandle: { $in: doc.following } } );
followingCursor.each(function (err, following) {
if(following != null) {
feed.push(following.tweets);
}
});
promise.resolve(feed);
}
In the above code, promise should be resolved if the following != null condition fails.
Apparently MongoDB driver returns null when the values in cursor end. The correct code is as following -
if (doc != null) {
var followingCursor = MongoDB.collection("users").find( { twitterHandle: { $in: doc.following } } );
followingCursor.each(function (err, following) {
if(following != null) {
feed = feed.concat(following.tweets);
} else {
promise.resolve(feed);
}
});
}

ES6 Classes for Data Models

I'm trying to use ES6 Classes to construct data models (from a MySQL database) in an API that I'm building. I prefer not using an ORM/ODM library, as this will be a very basic, simple API. But, I'm struggling to get my head around how to define these models.
My data entities are (these are just some simplified examples):
CUSTOMER
Data Model
id
name
groupId
status (enum of: active, suspended, closed)
Private Methods
_getState(status) {
var state = (status == 'active' ? 'good' : 'bad');
return state;
}
Requests
I want to be able to do:
findById: Providing a single customer.id, return the data for that specific customer, i.e. SELECT * FROM customers WHERE id = ?
findByGroupId: Providing a group.id, return the data for all the customers (in an array of objects), belonging to that group, i.e. SELECT * FROM customers WHERE groupId = ?
Response Payloads
For each customer object, I want to return JSON like this:
findById(1);:
[{
"id" : 1,
"name" : "John Doe",
"groupId" : 2,
"status" : "active",
"state" : "good"
}]
findByGroupId(2);:
[{
"id" : 1,
"name" : "John Doe",
"groupId" : 2,
"status" : "active",
"state" : "good"
},
{
"id" : 4,
"name" : "Pete Smith",
"groupId" : 2,
"status" : "suspended",
"state" : "bad"
}]
GROUP
Data Model
id
title
Requests
I want to be able to do:
findById: Providing a single group.id, return the data for that specific group, i.e. SELECT * FROM groups WHERE id = ?
Response Payloads
For each group object, I want to return JSON like this:
findById(2);:
{
"id" : 2,
"title" : "This is Group 2",
"customers" : [{
"id" : 1,
"name" : "John Doe",
"groupId" : 2,
"status" : "active",
"state" : "good"
},
{
"id" : 4,
"name" : "Pete Smith",
"groupId" : 2,
"status" : "suspended",
"state" : "bad"
}]
}
Requirements:
Must use ES6 Classes
Each model in its own file (e.g. customer.js) to be exported
Questions:
My main questions are:
Where would I define the data structure, including fields that require data transformation, using the private methods (e.g. _getState())
Should the findById, findByGroupId, etc by defined within the scope of the class? Or, should these by separate methods (in the same file as the class), that would instantiate the object?
How should I deal with the case where one object is a child of the other, e.g. returning the Customer objects that belongs to a Group object as an array of objects in the Group's findById?
Where should the SQL queries that will connect to the DB be defined? In the getById, getByGroupId, etc?
UPDATE!!
This is what I came up with - (would be awesome if someone could review, and comment):
CUSTOMER Model
'use strict';
class Cust {
constructor (custData) {
this.id = custData.id;
this.name = custData.name;
this.groupId = custData.groupId;
this.status = custData.status;
this.state = this._getState(custData.status);
}
_getState(status) {
let state = (status == 'active' ? 'good' : 'bad');
return state;
}
}
exports.findById = ((id) => {
return new Promise ((resolve, reject) => {
let custData = `do the MySQL query here`;
let cust = new Cust (custData);
let Group = require(appDir + process.env.PATH_API + process.env.PATH_MODELS + 'group');
Group.findById(cust.groupId).then(
(group) => {
cust.group = group;
resolve (cust)
},
(err) => {
resolve (cust);
}
);
});
});
GROUP Model
'use strict';
class Group {
constructor (groupData) {
this.id = groupData.id;
this.title = groupData.title;
}
}
exports.findById = ((id) => {
return new Promise ((resolve, reject) => {
let groupData = `do the MySQL query here`;
if (id != 2){
reject('group - no go');
};
let group = new Group (groupData);
resolve (group);
});
});
CUSTOMER Controller (where the Customer model is instantiated)
'use strict';
var Cust = require(appDir + process.env.PATH_API + process.env.PATH_MODELS + 'cust');
class CustController {
constructor () {
}
getCust (req, res) {
Cust.findById(req.params.id).then(
(cust) => {
res(cust);
},
(err) => {
res(err);
}
)
}
}
module.exports = CustController;
This seems to be working well, and I've been able to use Class, Promise and let to make it more ES6 friendly.
So, I'd like to get some input on my approach. Also, am I using the export and required features correctly in this context?

Here is another approach,
Where would I define the data structure, including fields that require data transformation, using the private methods (e.g. _getState())
You should define those fields, relationship in your model class extending the top model. Example:
class Group extends Model {
attributes() {
return {
id: {
type: 'integer',
primary: true
},
title: {
type: 'string'
}
};
}
relationships() {
return {
'Customer': {
type: 'hasMany',
foreignKey: 'groupId'
}
};
}
}
Should the findById, findByGroupId, etc by defined within the scope of the class? Or, should these by separate methods (in the same file as the class), that would instantiate the object?
Instead of having many functions use findByAttribute(attr) in Model Example:
static findByAttribute(attr) {
return new Promise((resolve, reject) => {
var query = this._convertObjectToQueriesArray(attr);
query = query.join(" and ");
let records = `SELECT * from ${this.getResourceName()} where ${query}`;
var result = this.run(records);
// Note: Only support 'equals' and 'and' operator
if (!result) {
reject('Could not found records');
} else {
var data = [];
result.forEach(function(record) {
data.push(new this(record));
});
resolve(data);
}
});
}
/**
* Convert Object of key value to sql filters
*
* #param {Object} Ex: {id:1, name: "John"}
* #return {Array of String} ['id=1', 'name=John']
*/
static _convertObjectToQueriesArray(attrs) {
var queryArray = [];
for (var key in attrs) {
queryArray.push(key + " = " + attrs[key]);
}
return queryArray;
}
/**
* Returns table name or resource name.
*
* #return {String}
*/
static getResourceName() {
if (this.resourceName) return this.resourceName();
if (this.constructor.name == "Model") {
throw new Error("Model is not initialized");
}
return this.constructor.name.toLowerCase();
}
How should I deal with the case where one object is a child of the other, e.g. returning the Customer objects that belongs to a Group object as an array of objects in the Group's findById?
In case of relationships, you should have methods like findRelations, getRelatedRecords.
var customer1 = new Customer({ id: 1, groupId: 3});
customer1.getRelatedRecords('Group');
class Model {
...
getRelatedRecords(reln) {
var targetRelationship = this.relationships()[reln];
if (!targetRelationship) {
throw new Error("No relationship found.");
}
var primaryKey = this._getPrimaryKey();
var relatedObject = eval(reln);
var attr = {};
if (targetRelationship.type == "hasOne") {
console.log(this.values);
attr[relatedObject.prototype._getPrimaryKey()] = this.values[targetRelationship.foreignKey];
} else if (targetRelationship.type == "hasMany") {
attr[targetRelationship.foreignKey] = this.values[this._getPrimaryKey()];
}
relatedObject.findByAttribute(attr).then(function(records) {
// this.values[reln] = records;
});
}
...
}
Where should the SQL queries that will connect to the DB be defined? In the getById, getByGroupId, etc?
This one is tricky, but since you want your solution to be simple put the queries inside your find methods. Ideal scenario will be to have their own QueryBuilder Class.
Check the following full code the solution is not fully functional but you get the idea. I've also added engine variable in the model which you can use to enhance fetching mechanism. All other design ideas are upto your imagination :)
FULL CODE:
var config = {
engine: 'db' // Ex: rest, db
};
class Model {
constructor(values) {
this.values = values;
this.engine = config.engine;
}
toObj() {
var data = {};
for (var key in this.values) {
if (this.values[key] instanceof Model) {
data[key] = this.values[key].toObj();
} else if (this.values[key] instanceof Array) {
data[key] = this.values[key].map(x => x.toObj());
} else {
data[key] = this.values[key];
}
}
return data;
}
static findByAttribute(attr) {
return new Promise((resolve, reject) => {
var query = this._convertObjectToQueriesArray(attr);
query = query.join(" and ");
let records = `SELECT * from ${this.getResourceName()} where ${query}`;
var result = this.run(records);
// Note: Only support 'equals' and 'and' operator
if (!result) {
reject('Could not found records');
} else {
var data = [];
result.forEach(function(record) {
data.push(new this(record));
});
resolve(data);
}
});
}
getRelatedRecords(reln) {
var targetRelationship = this.relationships()[reln];
if (!targetRelationship) {
throw new Error("No relationship found.");
}
var primaryKey = this._getPrimaryKey();
var relatedObject = eval(reln);
var attr = {};
if (targetRelationship.type == "hasOne") {
console.log(this.values);
attr[relatedObject.prototype._getPrimaryKey()] = this.values[targetRelationship.foreignKey];
} else if (targetRelationship.type == "hasMany") {
attr[targetRelationship.foreignKey] = this.values[this._getPrimaryKey()];
}
relatedObject.findByAttribute(attr).then(function(records) {
// this.values[reln] = records;
});
}
/**
* Test function to show what queries are being ran.
*/
static run(query) {
console.log(query);
return [];
}
_getPrimaryKey() {
for (var key in this.attributes()) {
if (this.attributes()[key].primary) {
return key;
}
}
}
/**
* Convert Object of key value to sql filters
*
* #param {Object} Ex: {id:1, name: "John"}
* #return {Array of String} ['id=1', 'name=John']
*/
static _convertObjectToQueriesArray(attrs) {
var queryArray = [];
for (var key in attrs) {
queryArray.push(key + " = " + attrs[key]);
}
return queryArray;
}
/**
* Returns table name or resource name.
*
* #return {String}
*/
static getResourceName() {
if (this.resourceName) return this.resourceName();
if (this.constructor.name == "Model") {
throw new Error("Model is not initialized");
}
return this.constructor.name.toLowerCase();
}
}
class Customer extends Model {
attributes() {
return {
id: {
type: 'integer',
primary: true
},
name: {
type: 'string'
},
groupId: {
type: 'integer'
},
status: {
type: 'string'
},
state: {
type: 'string'
}
};
}
relationships() {
return {
'Group': {
type: 'hasOne',
foreignKey: 'groupId'
}
};
}
}
class Group extends Model {
attributes() {
return {
id: {
type: 'integer',
primary: true
},
title: {
type: 'string'
}
};
}
relationships() {
return {
'Customer': {
type: 'hasMany',
foreignKey: 'groupId'
}
};
}
}
var cust = new Customer({
id: 1,
groupId: 3
});
cust.getRelatedRecords('Group');
var group = new Group({
id: 3,
title: "Awesome Group"
});
group.getRelatedRecords('Customer');
var groupData = new Group({
"id": 2,
"title": "This is Group 2",
"customers": [new Customer({
"id": 1,
"name": "John Doe",
"groupId": 2,
"status": "active",
"state": "good"
}),
new Customer({
"id": 4,
"name": "Pete Smith",
"groupId": 2,
"status": "suspended",
"state": "bad"
})
]
});
console.log(groupData.toObj());