GraphQL is a data "query language created by Facebook in 2015 for describing the capabilities and requirements of data models for client‐server applications". The GraphQL specification can be read on their hosted GitHub. A cliff notes version is described on GraphQL's GitHub. To learn more about the GraphQL language, I highly recommend GraphQL's website.
This package pulls inspiration from graphql-js and Mathew Mueller's graph.ql. I wanted the full functionality of GraphQL, but I didn't want to force users to write full object definitions when can already be defined with GraphQL syntax.
gqlr merges R's rapid development speed with the consistent query language of GraphQL.
# The development version from GitHub:
# install.packages("devtools")
devtools::install_github("schloerke/gqlr")If you encounter a clear bug, please file a minimal reproducible example on GitHub.
library(magrittr)
library(gqlr)
schema <- "
type Hello {
world: String
}
schema {
query: Hello
}
" %>%
gqlr_schema()
execute_request("{world}", schema, initial_value = list(world = "Hi!"))
# {
# "data": {
# "world": "Hi!"
# }
# }
add_human <- function(human_data, id, name, appear, home, friend) {
human <- list(id = id, name = name, appearsIn = appear, friends = friend, homePlanet = home)
# set up a function to be calculated if the field totalCredits is required
human$totalCredits <- function(obj, args, schema) {
length(human$appearsIn)
}
human_data[[id]] <- human
human_data
}
add_droid <- function(droid_data, id, name, appear, pf, friend) {
droid <- list(id = id, name = name, appearsIn = appear, friends = friend, primaryFunction = pf)
# set extra fields manually
droid$totalCredits <- length(droid$appearsIn)
droid_data[[id]] <- droid
droid_data
}
human_data <- list() %>%
add_human("1000", "Luke Skywalker", c(4, 5, 6), "Tatooine", c("1002", "1003", "2000", "2001")) %>%
add_human("1002", "Han Solo", c(4, 5, 6), "Corellia", c("1000", "1003", "2001")) %>%
add_human("1003", "Leia Organa", c(4, 5, 6), "Alderaan", c("1000", "1002", "2000", "2001"))
droid_data <- list() %>%
add_droid("2000", "C-3PO", c(4, 5, 6), "Protocol", c("1000", "1002", "1003", "2001")) %>%
add_droid("2001", "R2-D2", c(4, 5, 6), "Astromech", c("1000", "1002", "1003"))
all_characters <- list() %>% append(human_data) %>% append(droid_data)
all_characters[[1]]
# $id
# [1] "1000"
#
# $name
# [1] "Luke Skywalker"
#
# $appearsIn
# [1] 4 5 6
#
# $friends
# [1] "Tatooine"
#
# $homePlanet
# [1] "1002" "1003" "2000" "2001"
#
# $totalCredits
# function (obj, args, schema)
# {
# length(human$appearsIn)
# }
# <environment: 0x7fadd8ca2038>"
enum Episode { NEWHOPE, EMPIRE, JEDI }
interface Character {
id: String!
name: String
friends: [Character]
appearsIn: [Episode]
}
type Droid implements Character {
id: String!
name: String
friends: [Character]
appearsIn: [Episode]
primaryFunction: String
}
type Human implements Character {
id: String!
name: String
friends: [Character]
appearsIn: [Episode]
homePlanet: String
}
type Query {
hero(episode: Episode): Character
human(id: String!): Human
droid(id: String!): Droid
}
# the schema type must be provided if a query or mutation is to be executed
schema {
query: Query
}
" %>%
gqlr_schema(
Episode = list(
resolve = function(episode_id, schema) {
switch(as.character(episode_id),
"4" = "NEWHOPE",
"5" = "EMPIRE",
"6" = "JEDI",
"UNKNOWN_EPISODE"
)
}
),
Character = list(
resolve_type = function(id, schema) {
ifelse(id %in% names(droid_data), "Droid", "Human")
}
),
Human = list(
# Add a resolve method for type Human that takes in an id and returns the human data
resolve = function(id, args, schema) {
human_data[[id]]
}
),
Droid = list(
# description for Droid
description = "A mechanical creature in the Star Wars universe.",
# Add a resolve method for type Droid that takes in an id and returns the droid data
resolve = function(id, schema) {
droid_data[[id]]
}
),
Query = function(null, schema) {
list(
# return a function for key 'hero'
# the id will be resolved by the appropriate resolve() method of Droid or Human
hero = function(obj, args, schema) {
episode <- args$episode
if (identical(episode, 5) || identical(episode, "EMPIRE")) {
"1000" # Luke
} else {
"2001" # R2-D2
}
},
# the id will be resolved by the Human resolve() method
human = function(obj, args, schema) {
args$id
},
# the id will be resolved by the Droid resolve() method
droid = function(obj, args, schema) {
args$id
}
)
}
) ->
star_wars_schema# Use the resolve method to initialize the data
"
{
hero {
id
name
friends {
id
name
}
}
}
" %>%
execute_request(star_wars_schema)
# {
# "data": {
# "hero": {
# "id": "2001",
# "name": "R2-D2",
# "friends": [
# {
# "id": "1000",
# "name": "Luke Skywalker"
# },
# {
# "id": "1002",
# "name": "Han Solo"
# },
# {
# "id": "1003",
# "name": "Leia Organa"
# }
# ]
# }
# }
# }
# Use variables...
"
query FetchSomeIDQuery($someId: String!) {
human(id: $someId) {
name
}
}
" %>%
execute_request(star_wars_schema, variables = list(someId = "1000"))
# {
# "data": {
# "human": {
# "name": "Luke Skywalker"
# }
# }
# }
# Introspection
"
query IntrospectionTypeQuery {
__type(name: \"Droid\") {
kind
name
fields {
name
}
}
}
" %>%
execute_request(star_wars_schema)
# {
# "data": {
# "__type": {
# "kind": "OBJECT",
# "name": "Droid",
# "fields": [
# {
# "name": "id"
# },
# {
# "name": "name"
# },
# {
# "name": "friends"
# },
# {
# "name": "appearsIn"
# },
# {
# "name": "primaryFunction"
# },
# {
# "name": "__typename"
# }
# ]
# }
# }
# }# R
gqlr:::server(star_wars_schema, log = TRUE) # forgot to exportExplore with curl
# GET R2-D2 and his friends' names
curl '127.0.0.1:8000/graphql?query=%7Bhero%7Bname%7D%7D&pretty=TRUE'
# {
# "data": {
# "hero": {
# "name": "R2-D2"
# }
# }
# }
# POST for R2-D2 and his friends' names (no need to url escape the query)
curl --data '{"query":"{hero{name}}"}' '127.0.0.1:8000/graphql' # defaults to parse as JSON
# {"data":{"hero":{"name":"R2-D2"}}}
curl --data '{"query":"{hero{name}}"}' '127.0.0.1:8000/graphql' --header "Content-Type:application/json"
# {"data":{"hero":{"name":"R2-D2"}}}
curl --data '{hero{name}}' '127.0.0.1:8000/graphql' --header "Content-Type:application/graphql"
# {"data":{"hero":{"name":"R2-D2"}}}
# GET Schema definition
curl '127.0.0.1:8000/'
# enum Episode {
# NEWHOPE
# EMPIRE
# JEDI
# }
#
# type Droid implements Character {
# id: String!
# name: String
# friends: [Character]
# appearsIn: [Episode]
# primaryFunction: String
# }
#
# type Human implements Character {
# id: String!
# name: String
# friends: [Character]
# appearsIn: [Episode]
# homePlanet: String
# }
#
# type Query {
# hero(episode: Episode): Character
# human(id: String!): Human
# droid(id: String!): Droid
# }
#
# interface Character {
# id: String!
# name: String
# friends: [Character]
# appearsIn: [Episode]
# }
#
# schema {
# query: Query
# }