I'm using sails.js for a project and everything is going fine so far. Except that I don't know how to have an optional association between my two models. If I don't specify one, then if I use populate() it takes the first one available.
I have those two models:
// Book.js
module.exports = {
attributes: {
title: 'string',
serie: { model: 'serie' }
},
};
// Serie.js
module.exports = {
attributes: {
name: 'string',
books: { collection: 'book', via: 'serie' }
}
};
If I do this:
$ sails console
> Book.create({title: "Title"}).exec(function(err, book) {
Book.findOne({id: book.id }).populateAll().exec(function(err, book) {
console.log(book);
});
});
I get this:
{
serie: { name: 'Previously inserted serie' },
title: 'Title',
id: '55d6230122e3b1e70d877351'
}
Why isn't serie empty ? When inserting the book, I didn't specify any serie but it is still linked to a random one.
It was actually a bug from the sails-mongo adapter. I made a pull request that fixes it.
Related
Every tutorial I have found thus far has achieved pagination in GraphQL via Apollo, Relay, or some other magic framework. I was hoping to find answers in similar asked questions here but they don't exist. I understand how to setup the queries but I'm unclear as to how I would implement the resolvers.
Could someone point me in the right direction? I am using mongoose/MongoDB and ES5, if that helps.
EDIT: It's worth noting that the official site for learning GraphQL doesn't have an entry on pagination if you choose to use graphql.js.
EDIT 2: I love that there are some people who vote to close questions before doing their research whereas others use their knowledge to help others. You can't stop progress, no matter how hard you try. (:
Pagination in vanilla GraphQL
// Pagination argument type to represent offset and limit arguments
const PaginationArgType = new GraphQLInputObjectType({
name: 'PaginationArg',
fields: {
offset: {
type: GraphQLInt,
description: "Skip n rows."
},
first: {
type: GraphQLInt,
description: "First n rows after the offset."
},
}
})
// Function to generate paginated list type for a GraphQLObjectType (for representing paginated response)
// Accepts a GraphQLObjectType as an argument and gives a paginated list type to represent paginated response.
const PaginatedListType = (ItemType) => new GraphQLObjectType({
name: 'Paginated' + ItemType, // So that a new type name is generated for each item type, when we want paginated types for different types (eg. for Person, Book, etc.). Otherwise, GraphQL would complain saying that duplicate type is created when there are multiple paginated types.
fields: {
count: { type: GraphQLInt },
items: { type: new GraphQLList(ItemType) }
}
})
// Type for representing a single item. eg. Person
const PersonType = new GraphQLObjectType({
name: 'Person',
fields: {
id: { type: new GraphQLNonNull(GraphQLID) },
name: { type: GraphQLString },
}
})
// Query type which accepts pagination arguments with resolve function
const PersonQueryTypes = {
people: {
type: PaginatedListType(PersonType),
args: {
pagination: {
type: PaginationArgType,
defaultValue: { offset: 0, first: 10 }
},
},
resolve: (_, args) => {
const { offset, first } = args.pagination
// Call MongoDB/Mongoose functions to fetch data and count from database here.
return {
items: People.find().skip(offset).limit(first).exec()
count: People.count()
}
},
}
}
// Root query type
const QueryType = new GraphQLObjectType({
name: 'QueryType',
fields: {
...PersonQueryTypes,
},
});
// GraphQL Schema
const Schema = new GraphQLSchema({
query: QueryType
});
and when querying:
{
people(pagination: {offset: 0, first: 10}) {
items {
id
name
}
count
}
}
Have created a launchpad here.
There's a number of ways you could implement pagination, but here's two simple example resolvers that use Mongoose to get you started:
Simple pagination using limit and skip:
(obj, { pageSize = 10, page = 0 }) => {
return Foo.find()
.skip(page*pageSize)
.limit(pageSize)
.exec()
}
Using _id as a cursor:
(obj, { pageSize = 10, cursor }) => {
const params = cursor ? {'_id': {'$gt': cursor}} : undefined
return Foo.find(params).limit(pageSize).exec()
}
I have a model that has an attribute that is a collection association:
Take for example, a User model below.
module.exports = {
attributes: {
pets: {
collection: 'pet'
}
}
}
I am aware that I can add pets to a user instance with
user.pets.add(3);
But how could I replace any existing pets with a new group of pets??
Ok I've been playing with the API and found an answer. The following call should update (set) the pets association for a single user. If there were existing pets, this approach would override them.
User.update({id:1}, {pets: [{id: 7}, {id: 8}]}).exec(cb);
You'd remove all the existing pets and create new ones. sails.js has no single special API function to do what you are trying to do, but it's pretty simple either way:
var newPets = [
{ name: 'fluffy', user: 1 },
...
];
Pet.destroy({ user: 1 })
.then(function () {
return _.map(newPets, Pet.create);
})
.then(function (pets) {
// pets are "replaced"
});
Or something like that.
I found this example to use the Node API to apply filters to related models, but I was wondering if it was possible to achieve the same result using REST?
Node Example:
Post.find({
include: {
relation: 'owner', // include the owner object
scope: { // further filter the owner object
fields: ['username', 'email'], // only show two fields
include: { // include orders for the owner
relation: 'orders',
scope: {
where: {orderId: 5} // only select order with id 5
}
}
}
}
}, function() { ... });
The closest version of a REST url I can get to work is:
...?filter[include][owners][orders]
Is it possible to create a REST url that behaves the same way as the above Node example, by limiting the results based on a related model filter... in this case orders?
I have this functions so when I call the Hdates/coming REST API it shows the events with date greater than today and also includes the venues... Hope it helps.
Hdate.coming = function(cb) {
Hdate.find({
where : {
event_date :{gt: Date.now()}
},
include : {
relation: 'event',
scope : {
include: {
relation: 'venue'
}
}
}
}, cb);
};
Hdate.setup = function() {
Hdate.base.setup.apply(this, arguments);
this.remoteMethod('coming', {
description: 'Find Coming Events by Date',
returns: {arg: 'events', root: true},
http: { verb: 'GET' }
});
};
Hdate.setup();
Hy there,
Before going to the hacky / cutom way i wanted to know if there is a built in query way to check for an empty / non empty many to many relationship as i was not successfull neither on google nor the doc.
If i take the example in the doc let's imagine i want to retrive a user only if he has a a Pet or Retrive a Pet without any Owner through a query.
// A user may have many pets
var User = Waterline.Collection.extend({
identity: 'user',
connection: 'local-postgresql',
attributes: {
firstName: 'string',
lastName: 'string',
// Add a reference to Pet
pets: {
collection: 'pet',
via: 'owners',
dominant: true
}
}
});
// A pet may have many owners
var Pet = Waterline.Collection.extend({
identity: 'pet',
connection: 'local-postgresql',
attributes: {
breed: 'string',
type: 'string',
name: 'string',
// Add a reference to User
owners: {
collection: 'user',
via: 'pets'
}
}
});
P.s. i know how to filter results after query execution that's not what i'm asking :)
There is nothing built in (aka User.hasPet() ) or something like that., so the simple answer is NO
If I know of these issues before hand I tend to write my DB in such a way that the queries are fast. IE: the User schema would have a hasPets column. Whenever a pet is added/removed a callbacks hits the user table to mark that field if it has an owner or not. So then I can query User.findAll({hasPet:true}).
Its a little much, but it depends on where you speed is needed.
This is a bit late, but I wanted to let you know it's pretty easy to do this with the Waterline ORM lifecycle functions. I've done it in a few of my projects. Basically, use the beforeCreate and beforeUpdate functions to set your flags. For your user, it might look like...
var User = Waterline.Collection.extend({
identity: 'user',
connection: 'local-postgresql',
beforeCreate: function(values, next) {
if (values.pets) {
values.has_pet = true;
} else {
values.has_pet = false;
}
next();
}
beforeUpdate: function(values, next) {
if (values.pets) {
values.has_pet = true;
} else {
values.has_pet = false;
}
next();
}
attributes: {
firstName: 'string',
lastName: 'string',
// Add a reference to Pet
pets: {
collection: 'pet',
via: 'owners',
dominant: true
},
has_pet: {
type: 'boolean'
}
}
});
Then you can query based on the has_pet attribute
I am trying to give a default association from a user to a pet, whenever a new User created.
Model:: User.js
var User = {
attributes: {
name: {type: 'string'},
// Add a One Way Relation to pet model
pets: {
collection: 'pet'
},
},
/*** This did not work ***/
beforeCreate: function (user, next) {
var defaultPet = {name: 'Default Pet 1'};
Pet.find(defaultPet).exec(function(err, pet) {
user.name = "BEFORECREATE",
user.pets = pet[0].id;
next();
});
},
}
module.exports = User;
However when a new record is created the user.pet is [ ], but user.name is changed to "BEFORECREATE".
How do I get user.pets = [{name: 'Default Pet 1'}] automatically for the new user created?
Or is there a better place for setting such defaults?
----- UPDATE: More info
I am using sails-disk currently.
Model: Pet.js
module.exports = {
attributes: {
name: {
type: 'string',
required: true
}
}
};
You can't add associations to a model in a lifecycle callback like beforeCreate. Currently, Waterline looks for and processes "nested models" like these before lifecycle callbacks run, so by the time beforeCreate is called it's too late. The simplest solution would be to create a User.createUser class method that wraps the logic you want:
createUser: function(data, cb) {
// If there are already pets specified, just use those
if (data.pets) {return User.create(data).exec(cb);}
// Otherwise look up the default pet
Pet.findOne({name:"Default Pet 1"}).exec(function(err,pet) {
// Return in case of error
if (err) {return cb(err);}
// Assuming the default pet exists, attach it
if (pet) {
console.log("SETTING DEFAULT PET", pet.id);
data.pets = [pet.id];
}
// Create the pet
return User.create(data).exec(cb);
});
}
A few notes:
In your example you were setting pets directly to an ID, but since it's a collection you must set it to an array.
If you're using the sails-disk adapter, you'll need to set schema: true in your model for this to work.
The new User model you get back will not be populated; you'll have to do a find with a populate('pets') with the new User ID to get the pet data attached.