graphql-fields-projection-v2
v1.0.1
Published
- [Why using this?](#why-using-this) - [Install](#install) - [How to](#how-to) - [Example 1: simplest usecase](#example-1-simplest-usecase) - [Example 2: Get more fields](#example-2-get-more-fields) - [Example 3: Get child path](#example-3-get-child
Downloads
5
Maintainers
Readme
GraphQL Fields Projection
This library create field projection from GraphQL query
NOTE: Since version 1.1.0 the default returnType is string
Why using this?
There are many libraries can do the same function. However, starting in MongoDB 4.4, the Path Collision Restrictions are introduced . And it is illegal to project an embedded document with any of the embedded document's fields:
db.inventory.find({}, { size: 1, "size.uom": 1 }); // Invalid starting in 4.4
- And this library is created to remove the collision.
- This library can work with dataloader also
Install
npm install graphql-fields-projection-v2
How to
Please see the following examples
Example 1: simplest usecase
Given the following query
query user {
user(id: 123) {
id
address
info {
firstName
lastName
}
}
}
const { createSelectedFields } = require('graphql-fields-projection');
resolve(parent, args, context, info){
const selectedFields = createSelectedFields(info); // 'id address info.firstName info.lastName'
}
Example 2: Get more fields
Given the following query
query user {
user(id: 123) {
id
address
info {
firstName
lastName
}
}
}
const { createSelectedFields } = require('graphql-fields-projection');
resolve(parent, args, context, info){
// Now you like to get more fields for further resolve: `timezone`, and `info` object
const selectedFields = createSelectedFields(info, { additionalFields: ['info', 'address', 'timezone'] }); // 'id info timezone'
}
Example 3: Get child path
Given the following query
query purchase {
purchase(id: 123) {
id
buyer {
id
address
info {
firstName
lastName
}
}
product {
id
# ...others
}
}
}
const { createSelectedFields } = require('graphql-fields-projection');
resolve(parent, args, context, info){
// Now you like to get selected fields of `buyer`
const selectedFields = createSelectedFields(info, { path: 'buyer' }); // 'id address info.firstName info.lastName'
// OR with additionalFields
const selectedFields2 = createSelectedFields(info, {
path: 'buyer', additionalFields: ['info', 'address', 'timezone'],
}); // 'id info timezone'
}
Example 4: returnTypes
NOTE: Since version 1.1.0 the default returnType is string
By the default the return result will be an string of projected fields. But you can also get the array or object
query user {
user(id: 123) {
id
address
info {
firstName
lastName
}
}
}
const { createSelectedFields } = require('graphql-fields-projection');
resolve(parent, args, context, info){
const resultString = createSelectedFields(info); // 'id address info.firstName info.lastName'
const resultString = createSelectedFields(info, { returnType : 'string' } ); // 'id address info.firstName info.lastName'
const resultArray2 = createSelectedFields(info, { returnType : 'array' }); // [ 'id', 'address', 'info.firstName', 'info.lastName' ]
const resultObject = createSelectedFields(info, { returnType : 'object' }); // { id: 1, address: 1, 'info.firstName': 1, 'info.lastName': 1 }
}
Example 5: Using with Dataloader
query purchase {
purchase(id: 123) {
id
buyer {
id
address
info {
firstName
lastName
}
}
products {
id
sku
name
price
}
}
}
const { createSelectedFields, createMergedSelectedFields } = require('graphql-fields-projection');
// This is an example with Apollo Federation, but you can run with any resolvers
__resolveReference(parent, context, info) {
const { loaders } = context;
const selectedFields = createSelectedFields(info, { returnType : 'array' });
return loaders.product.load(JSON.stringify({ id: parent.id, selectedFields }));
}
// The implementation of `loaders.product()`
async function batchProducts(keys) {
const { ids: productIds, selectedFields } = createMergedSelectedFields(keys);
const products = await Product.find({ _id: { $in: productIds } })
.select(selectedFields)
.lean();
// Don't forget mapping results
// ...
return products;
}
The function createMergedSelectedFields()
supports the following options: