Graphlient
A friendlier Ruby client for consuming GraphQL-based APIs. Built on top of your usual graphql-client, but with better defaults, more consistent error handling, and using the faraday HTTP client.
Table of Contents
Installation
Add the following line to your Gemfile.
gem 'graphlient'
Usage
Create a new instance of Graphlient::Client
with a URL and optional headers/http_options.
client = Graphlient::Client.new('https://test-graphql.biz/graphql',
headers: {
'Authorization' => 'Bearer 123'
},
http_options: {
read_timeout: 20,
write_timeout: 30
}
)
http_options | default | type |
---|
read_timeout | nil | seconds |
write_timeout | nil | seconds |
The schema is available automatically via .schema
.
client.schema
Make queries with query
, which takes a String or a block for the query definition.
With a String.
response = client.query <<~GRAPHQL
query {
invoice(id: 10) {
id
total
line_items {
price
item_type
}
}
}
GRAPHQL
With a block.
response = client.query do
query do
invoice(id: 10) do
id
total
line_items do
price
item_type
end
end
end
end
This will call the endpoint setup in the configuration with POST
, the Authorization
header and query
as follows.
query {
invoice(id: 10) {
id
total
line_items {
price
item_type
}
}
}
A successful response object always contains data which can be iterated upon. The following example returns the first line item's price.
response.data.invoice.line_items.first.price
You can also execute mutations the same way.
response = client.query do
mutation do
createInvoice(input: { fee_in_cents: 12_345 }) do
id
fee_in_cents
end
end
end
The successful response contains data in response.data
. The following example returns the newly created invoice's ID.
response.data.create_invoice.first.id
Schema storing and loading on disk
To reduce requests to graphql API you can cache schema:
client = Client.new(url, schema_path: 'config/your_graphql_schema.json')
client.schema.dump!
Preloading Schema Once
Even if caching the schema on disk, instantiating Graphlient::Client
often can be both time and memory intensive due to loading the schema for each instance. This is especially true if the schema is a large file. To get around these performance issues, instantiate your schema once and pass it in as a configuration option.
One time in an initializer
schema = Graphlient::Schema.new(
'https://graphql.foo.com/graphql', 'lib/graphql_schema_foo.json'
)
Pass in each time you initialize a client
client = Graphlient::Client.new(
'https://graphql.foo.com/graphql',
schema: schema,
headers: {
'Authorization' => 'Bearer 123',
}
)
Error Handling
Unlike graphql-client, Graphlient will always raise an exception unless the query has succeeded.
All errors inherit from Graphlient::Errors::Error
if you need to handle them in bulk.
Executing Parameterized Queries and Mutations
Graphlient can execute parameterized queries and mutations by providing variables as query parameters.
The following query accepts an array of IDs.
With a String.
query = <<-GRAPHQL
query($ids: [Int]) {
invoices(ids: $ids) {
id
fee_in_cents
}
}
GRAPHQL
variables = { ids: [42] }
client.query(query, variables)
With a block.
client.query(ids: [42]) do
query(ids: [:int]) do
invoices(ids: :ids) do
id
fee_in_cents
end
end
end
Graphlient supports following Scalar types for parameterized queries by default:
:id
maps to ID
:boolean
maps to Boolean
:float
maps to Float
:int
maps to Int
:string
maps to String
You can use any of the above types with !
to make it required or use them in []
for array parameters.
For any other custom types, graphlient will simply use to_s
of the symbol provided for the type, so query(ids: [:InvoiceType!])
will result in query($ids: [InvoiceType!])
.
The following mutation accepts a custom type that requires fee_in_cents
.
client.query(input: { fee_in_cents: 12_345 }) do
mutation(input: :createInvoiceInput!) do
createInvoice(input: :input) do
id
fee_in_cents
end
end
end
Parse and Execute Queries Separately
You can parse
and execute
queries separately with optional variables. This is highly recommended as parsing a query and validating a query on every request adds performance overhead. Parsing queries early allows validation errors to be discovered before request time and avoids many potential security issues.
query = client.parse do
query(ids: [:int]) do
invoices(ids: :ids) do
id
fee_in_cents
end
end
end
client.execute query, ids: [42]
Or pass in a string instead of a block:
query = client.parse <<~GRAPHQL
query($some_id: Int) {
invoice(id: $some_id) {
id
feeInCents
}
}
GRAPHQL
client.execute query, ids: [42]
Dynamic vs. Static Queries
Graphlient uses graphql-client, which recommends building queries as static module members along with dynamic variables during execution. This can be accomplished with graphlient the same way.
Create a new instance of Graphlient::Client
with a URL and optional headers.
module SWAPI
Client = Graphlient::Client.new('https://test-graphql.biz/graphql',
headers: {
'Authorization' => 'Bearer 123'
},
allow_dynamic_queries: false
)
end
The schema is available automatically via .schema
.
SWAPI::Client.schema
Define a query.
module SWAPI
InvoiceQuery = Client.parse do
query(id: :int) do
invoice(id: :id) do
id
fee_in_cents
end
end
end
end
Execute the query.
response = SWAPI::Client.execute(SWAPI::InvoiceQuery, id: 42)
Note that in the example above the client is created with allow_dynamic_queries: false
(only allow static queries), while graphlient defaults to allow_dynamic_queries: true
(allow dynamic queries). This option is marked deprecated, but we're proposing to remove it and default it to true
in graphql-client#128.
Generate Queries with Graphlient::Query
You can directly use Graphlient::Query
to generate raw GraphQL queries.
query = Graphlient::Query.new do
query do
invoice(id: 10) do
line_items
end
end
end
query.to_s
Use of Fragments
Fragments should be referred by constant:
module Fragments
Invoice = client.parse <<~'GRAPHQL'
fragment on Invoice {
id
feeInCents
}
GRAPHQL
end
Graphlient
offers the syntax below to refer to the original constant:
- Triple underscore
___
to refer to the fragment - Double underscore
__
for namespace separator
In this example, Fragments::Invoice
would be referred as follows:
invoice_query = client.parse do
query do
invoice(id: 10) do
id
___Fragments__Invoice
end
end
end
The wrapped response only allows access to fields that have been explicitly asked for.
In this example, while id
has been referenced directly in the main query, feeInCents
has been spread via fragment and trying to access it in the original wrapped response will throw GraphQL::Client::ImplicitlyFetchedFieldError
(to prevent data leaks between components).
response = client.execute(invoice_query)
result = response.data.invoice
result.to_h
result.id
result.fee_in_cents
feeInCents
cannot be fetched directly from the main query, but from the fragment as shown below:
invoice = Fragments::Invoice.new(result)
invoice.id
invoice.fee_in_cents
Create API Client Classes with Graphlient::Extension::Query
You can include Graphlient::Extensions::Query
in your class. This will add a new method_missing
method to your context which will be used to generate GraphQL queries.
include Graphlient::Extensions::Query
query = query do
invoice(id: 10) do
line_items
end
end
query.to_s
Swapping the HTTP Stack
You can swap the default Faraday adapter for Net::HTTP
.
client = Graphlient::Client.new('https://test-graphql.biz/graphql',
http: Graphlient::Adapters::HTTP::HTTPAdapter
)
Testing with Graphlient and RSpec
Use Graphlient inside your RSpec tests in a Rails application or with Rack::Test
against your actual application.
require 'spec_helper'
describe App do
include Rack::Test::Methods
def app
end
let(:client) do
Graphlient::Client.new('http://test-graphql.biz/graphql') do |client|
client.http do |h|
h.connection do |c|
c.adapter Faraday::Adapter::Rack, app
end
end
end
end
context 'an invoice' do
let(:result) do
client.query do
query do
invoice(id: 10) do
id
end
end
end
end
it 'can be retrieved' do
expect(result.data.invoice.id).to eq 10
end
end
end
Alternately you can stub_request
with Webmock.
describe App do
let(:url) { 'http://example.com/graphql' }
let(:client) { Graphlient::Client.new(url) }
before do
stub_request(:post, url).to_return(
status: 200,
body: DummySchema.execute(GraphQL::Introspection::INTROSPECTION_QUERY).to_json
)
end
it 'retrieves schema' do
expect(client.schema).to be_a Graphlient::Schema
end
end
In order to stub the response to actual queries, dump the schema into a JSON file and specify it via schema_path as follows.
describe App do
let(:url) { 'http://graph.biz/graphql' }
let(:client) { Graphlient::Client.new(url, schema_path: 'spec/support/fixtures/invoice_api.json') }
let(:query) do
<<~GRAPHQL
query{
invoice(id: 42) {
id
feeInCents
}
}
GRAPHQL
end
let(:json_response) do
{
'data' => {
'invoice' => {
'id' => '42',
'feeInCents' => 2000
}
}
}.to_json
end
before do
stub_request(:post, url).to_return(
status: 200,
body: json_response
)
end
it 'returns invoice fees' do
response = client.query(query)
expect(response.data).to be_truthy
expect(response.data.invoice.id).to eq('42')
expect(response.data.invoice.fee_in_cents).to eq(2000)
end
end
License
MIT License, see LICENSE