The two types of objects seem to be so close to one another that having both feels redundant. What is the point of having both schemas and models?
EDIT: Although this has been useful for many people, as mentioned in the comments it answers the "how" rather than the why. Thankfully, the why of the question has been answered elsewhere also, with this answer to another question. This has been linked in the comments for some time but I realise that many may not get that far when reading.
Often the easiest way to answer this type of question is with an example. In this case, someone has already done it for me :)
Take a look here:
http://rawberg.com/blog/nodejs/mongoose-orm-nested-models/
EDIT: The original post (as mentioned in the comments) seems to no longer exist, so I am reproducing it below. Should it ever return, or if it has just moved, please let me know.
It gives a decent description of using schemas within models in mongoose and why you would want to do it, and also shows you how to push tasks via the model while the schema is all about the structure etc.
Original Post:
Let’s start with a simple example of embedding a schema inside a model.
var TaskSchema = new Schema({
name: String,
priority: Number
});
TaskSchema.virtual('nameandpriority')
.get( function () {
return this.name + '(' + this.priority + ')';
});
TaskSchema.method('isHighPriority', function() {
if(this.priority === 1) {
return true;
} else {
return false;
}
});
var ListSchema = new Schema({
name: String,
tasks: [TaskSchema]
});
mongoose.model('List', ListSchema);
var List = mongoose.model('List');
var sampleList = new List({name:'Sample List'});
I created a new TaskSchema object with basic info a task might have. A Mongoose virtual attribute is setup to conveniently combine the name and priority of the Task. I only specified a getter here but virtual setters are supported as well.
I also defined a simple task method called isHighPriority to demonstrate how methods work with this setup.
In the ListSchema definition you’ll notice how the tasks key is configured to hold an array of TaskSchema objects. The task key will become an instance of DocumentArray which provides special methods for dealing with embedded Mongo documents.
For now I only passed the ListSchema object into mongoose.model and left the TaskSchema out. Technically it's not necessary to turn the TaskSchema into a formal model since we won’t be saving it in it’s own collection. Later on I’ll show you how it doesn’t harm anything if you do and it can help to organize all your models in the same way especially when they start spanning multiple files.
With the List model setup let’s add a couple tasks to it and save them to Mongo.
var List = mongoose.model('List');
var sampleList = new List({name:'Sample List'});
sampleList.tasks.push(
{name:'task one', priority:1},
{name:'task two', priority:5}
);
sampleList.save(function(err) {
if (err) {
console.log('error adding new list');
console.log(err);
} else {
console.log('new list successfully saved');
}
});
The tasks attribute on the instance of our List model (sampleList) works like a regular JavaScript array and we can add new tasks to it using push. The important thing to notice is the tasks are added as regular JavaScript objects. It’s a subtle distinction that may not be immediately intuitive.
You can verify from the Mongo shell that the new list and tasks were saved to mongo.
db.lists.find()
{ "tasks" : [
{
"_id" : ObjectId("4dd1cbeed77909f507000002"),
"priority" : 1,
"name" : "task one"
},
{
"_id" : ObjectId("4dd1cbeed77909f507000003"),
"priority" : 5,
"name" : "task two"
}
], "_id" : ObjectId("4dd1cbeed77909f507000001"), "name" : "Sample List" }
Now we can use the ObjectId to pull up the Sample List and iterate through its tasks.
List.findById('4dd1cbeed77909f507000001', function(err, list) {
console.log(list.name + ' retrieved');
list.tasks.forEach(function(task, index, array) {
console.log(task.name);
console.log(task.nameandpriority);
console.log(task.isHighPriority());
});
});
If you run that last bit of code you’ll get an error saying the embedded document doesn’t have a method isHighPriority. In the current version of Mongoose you can’t access methods on embedded schemas directly. There’s an open ticket to fix it and after posing the question to the Mongoose Google Group, manimal45 posted a helpful work-around to use for now.
List.findById('4dd1cbeed77909f507000001', function(err, list) {
console.log(list.name + ' retrieved');
list.tasks.forEach(function(task, index, array) {
console.log(task.name);
console.log(task.nameandpriority);
console.log(task._schema.methods.isHighPriority.apply(task));
});
});
If you run that code you should see the following output on the command line.
Sample List retrieved
task one
task one (1)
true
task two
task two (5)
false
With that work-around in mind let’s turn the TaskSchema into a Mongoose model.
mongoose.model('Task', TaskSchema);
var Task = mongoose.model('Task');
var ListSchema = new Schema({
name: String,
tasks: [Task.schema]
});
mongoose.model('List', ListSchema);
var List = mongoose.model('List');
The TaskSchema definition is the same as before so I left it out. Once its turned into a model we can still access it’s underlying Schema object using dot notation.
Let’s create a new list and embed two Task model instances within it.
var demoList = new List({name:'Demo List'});
var taskThree = new Task({name:'task three', priority:10});
var taskFour = new Task({name:'task four', priority:11});
demoList.tasks.push(taskThree.toObject(), taskFour.toObject());
demoList.save(function(err) {
if (err) {
console.log('error adding new list');
console.log(err);
} else {
console.log('new list successfully saved');
}
});
As we’re embedding the Task model instances into the List we’re calling toObject on them to convert their data into plain JavaScript objects that the List.tasks DocumentArray is expecting. When you save model instances this way your embedded documents will contain ObjectIds.
The complete code example is available as a gist. Hopefully these work-arounds help smooth things over as Mongoose continues to develop. I’m still pretty new to Mongoose and MongoDB so please feel free to share better solutions and tips in the comments. Happy data modeling!
Schema is an object that defines the structure of any documents that will be stored in your MongoDB collection; it enables you to define types and validators for all of your data items.
Model is an object that gives you easy access to a named collection, allowing you to query the collection and use the Schema to validate any documents you save to that collection. It is created by combining a Schema, a Connection, and a collection name.
Originally phrased by Valeri Karpov, MongoDB Blog
I don't think the accepted answer actually answers the question that was posed. The answer doesn't explain why Mongoose has decided to require a developer to provide both a Schema and a Model variable. An example of a framework where they have eliminated the need for the developer to define the data schema is django--a developer writes up their models in the models.py file, and leaves it to the framework to manage the schema. The first reason that comes to mind for why they do this, given my experience with django, is ease-of-use. Perhaps more importantly is the DRY (don't repeat yourself) principle--you don't have to remember to update the schema when you change the model--django will do it for you! Rails also manages the schema of the data for you--a developer doesn't edit the schema directly, but changes it by defining migrations that manipulate the schema.
One reason I could understand that Mongoose would separate the schema and the model is instances where you would want to build a model from two schemas. Such a scenario might introduce more complexity than is worth managing--if you have two schemas that are managed by one model, why aren't they one schema?
Perhaps the original question is more a relic of the traditional relational database system. In world NoSQL/Mongo world, perhaps the schema is a little more flexible than MySQL/PostgreSQL, and thus changing the schema is more common practice.
To understand why? you have to understand what actually is Mongoose?
Well, the mongoose is an object data modeling library for MongoDB and Node JS, providing a higher level of abstraction. So it's a bit like the relationship between Express and Node, so Express is a layer of abstraction over regular Node, while Mongoose is a layer of abstraction over the regular MongoDB driver.
An object data modeling library is just a way for us to write Javascript code that will then interact with a database. So we could just use a regular MongoDB driver to access our database, it would work just fine.
But instead we use Mongoose because it gives us a lot more functionality out of the box, allowing for faster and simpler development of our applications.
So, some of the features Mongoose gives us schemas to model our data and relationship, easy data validation, a simple query API, middleware, and much more.
In Mongoose, a schema is where we model our data, where we describe the structure of the data, default values, and validation, then we take that schema and create a model out of it, a model is basically a wrapper around the schema, which allows us to actually interface with the database in order to create, delete, update, and read documents.
Let's create a model from a schema.
const tourSchema = new mongoose.Schema({
name: {
type: String,
required: [true, 'A tour must have a name'],
unique: true,
},
rating: {
type: Number,
default: 4.5,
},
price: {
type: Number,
required: [true, 'A tour must have a price'],
},
});
//tour model
const Tour = mongoose.model('Tour', tourSchema);
According to convetion first letter of a model name must be capitalized.
Let's create instance of our model that we created using mongoose and schema. also, interact with our database.
const testTour = new Tour({ // instance of our model
name: 'The Forest Hiker',
rating: 4.7,
price: 497,
});
// saving testTour document into database
testTour
.save()
.then((doc) => {
console.log(doc);
})
.catch((err) => {
console.log(err);
});
So having both schama and modle mongoose makes our life easier.
Think of Model as a wrapper to schemas. Schemas define the structure of your document , what kind of properties can you expect and what will be their data type (String,Number etc.). Models provide a kind of interface to perform CRUD on schema. See this post on FCC.
Schema basically models your data (where you provide datatypes for your fields) and can do some validations on your data. It mainly deals with the structure of your collection.
Whereas the model is a wrapper around your schema to provide you with CRUD methods on collections. It mainly deals with adding/querying the database.
Having both schema and model could appear redundant when compared to other frameworks like Django (which provides only a Model) or SQL (where we create only Schemas and write SQL queries and there is no concept of model). But, this is just the way Mongoose implements it.
I'm new to noSQL and i'm trying to figure out how to create the best possible model structure. What i need to do is every hour to retrieve leagues and matches from an api and add it to my database. Every hour the score might change and new matches might be added to each league and therefor this should be possible in the model. i've read the documentation and created following, however i'm not sure it is possible to update each and add new matches to leagues. What is the ideal modelling for such?
Tournament model
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var League = require('./league');
var TournamentSchema = new Schema({
slug: String,
tournaments: [League]
});
module.exports = mongoose.model('Tournament', TournamentSchema);
League
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var Match = require('./match');
var leagueSchema = new Schema({
leaguetId: Number,
name: String,
matches: [Match]
});
module.exports = mongoose.model('League', leagueSchema);
Match
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var matchSchema = new Schema({
homeTeam: String,
awayTeam: String,
homeScore: Number,
awayScore: Number,
start: Date
});
module.exports = mongoose.model('Match', matchSchema);
Post request so far
router.post('/tournaments', function(req, res, next) {
var tournament = new Tournament(); // create a new instance of the Bear model
tournament.name = req.body.slug; // set the bears name (comes from the request)
// save the bear and check for errors
tournament.save(function(err) {
if (err)
res.send(err);
res.json({ message: 'Tournament created!' });
});
});
If you're adding new matches to leagues and updating matches on a timed interval, why nest them within each other? Lets say you have a match with id 5 whose score changed. In order to find it to update it you'd have to first go through each league, and then iterate through each match in each league until you find the match with id 5. Unless I'm mistaken and there's some easier way to do it, this seems very inefficient.
Why not have two collections? A league collection and a match collection. There will be a 1 (league) : many (match) relationship. When you need to update a match's score, who cares what league it's in? Search the match collection for id 5, and update it.
What would a new match look like? Lets say a league with id 7 had a new match. Add a match to the match collection that has a league id of 7.
If you're really opposed to moving away from one collection.. at least store your matches in an object instead of an array, that way you can find matches with an O(1) lookup time by using it's match name. Instead of O(n) or O(n^2) lookup time like you currently have.
I read from mongoose documentation that it is possible to create custom schema types to be added to the ones already existing.
As suggested I tried to look into the mongoose-long example: https://github.com/aheckmann/mongoose-long
I need this in an application I am developing in which I have a profile that is a mongoose model. The profile has several fields such as name, surname and so on that are MultiValueField. A MultiValueField is on object with the following structure:
{
current : <string>
providers : <Array>
values : {
provider1 : value1,
provider2 : value2
}
}
The structure above has a list of allowed providers (ordered by priorities) from which the field's value can be retrieved. The current property keeps track of which provider is currently picked to use as value of the field. Finally the object values contains the values for each provider.
I have defined an object in node.js, whose constructor takes the structure above as argument and provides a lot of useful methods to set a new providers, adding values and so on.
Each field of my profile should be initialized with a different list of providers, but I haven't found a way yet to do so.
If I define MultiValueField as an Embedded Schema, I can do so only having each field as Array. Also I cannot initialize every field at the moment a profile is created with the list of providers.
I think the best solution is to define a SchemaType MultiValueFieldType, that has a cast function that returns a MultiValueField object. However, how can I define such a custom schema type? And how can I use custom options when defining it in the schema of the profile?
I already posted a question on mongoose Google group to ask how to create Custom Schema Types: https://groups.google.com/forum/?fromgroups#!topic/mongoose-orm/fCpxtKSXFKc
I was able to create custom schema types only as arrays too. You will be able to initialize the model, but this aproach has drawbacks:
You will have arrays even if you don't need them
If you use ParameterSchema on other model, you will need to replicate it
Custom Schema Type Code:
// Location has inputs and outputs, which are Parameters
// file at /models/Location.js
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ParameterSchema = new Schema({
name: String,
type: String,
value: String,
});
var LocationSchema = new Schema({
inputs: [ParameterSchema],
outputs: [ParameterSchema],
});
module.exports = mongoose.model('Location', LocationSchema);
To initialize the model:
// file at /routes/locations.js
var Location = require('../models/Location');
var location = { ... } // javascript object usual initialization
location = new Location(location);
location.save();
When this code runs, it will save the initialized location with its parameters.
I didn't understand all topics of your question(s), but I hope that this answer helps you.
I'm calling MongoDB from my Node app using Mongoose like this:
var query = itemModel.find();
query.exec(function (err, items) {
console.log(err);
socket.emit("items", items);
});
I have 3 models defined like this:
var Schema = mongoose.Schema
, ObjectId = Schema.ObjectId;
var playerModel = require('./models/player.js').make(Schema, mongoose);
var characterModel = require('./models/character.js').make(Schema, mongoose, ObjectId);
var itemModel = require('./models/item.js').make(Schema, mongoose);
my models look like this:
function make(Schema, mongoose) {
itemSchema = new Schema({
name: String
, bonus: [{
type: String
, value: Number
}]
, price: Number
, slot: String
});
return mongoose.model('Character', characterSchema);
}
exports.make = make;
For some reason I'm getting all documents, regardless of them being items, characters or players. Since I'm calling find() on itemModel I was expecting only Items, what am I doing wrong?
The model that you have shown appears to be the item model, but you are creating the model with the 'Character' name. This means that you told Mongoose about the scheme for an item and that it is stored in the 'character' collection. Assuming you've done the same for each other model (Character/Player), you've been Mongoose that everything is in the same collection.
Then you query that collection and you seem surprised that everything is stored in the same collection. It strikes me as if you have little experience with Mongoose/MongoDB, so I will suggest you download and learn to love MongoVUE. This application is a good GUI to see what is going on under the hood of the MongoDB database. While developing, you also might want to enable debugging so you can see what queries mongoose is launching to the server (mongoose.set('debug', true)).
I use mongoose in my node.js app, and basically have the following models:
// Define Car model
CarSchema = new Schema({
brand : String,
type: String,
maxSpeed : Number
});
mongoose.model('Car', CarSchema);
// Define User model
UserSchema = new Schema({
lastname : String,
firstname : String,
cars : [CarSchema]
});
mongoose.model('User', UserSchema);
I'm really new to NoSQL and I really want to give it a try but I first need to study if this really fits my needs.
With the above models, will I be able to create a query listing all the Users who have a particular type of car among their personal cars ?
I don't how to do it in mongoose. But in mongodb it possible. So, in mongodb shell query will looks like this:
db.users.find({"cars.type":"sport"})
Above query return all users thats have car with type 'sport' in their nested collection of cars.
Mongodb dot notation documentation.