数据库：一文掌握 GraphQL 的各种指令（GraphQL指令备忘）

这份快速参考备忘单提供了 GraphQL 的简要概述

入门

概述

• RESTful API 的另一种方法
• GraphQL 是一种 API 查询语言
• 使用清晰的共享术语轻松描述 GraphQL API 的形状。
• 客户端发出查询/突变以读取和更新数据
• GraphQL 语法可以表达复杂的实体关系
• 用 不同语言 实现 GraphQL 的库

参考：
GraphQL
GraphQL Schema Language Cheat Sheet (github.com)

Schema

:-	-
schema	GraphQL 架构定义
query	读取和遍历数据
mutation	修改数据或触发动作
subscription	发生事件时运行查询

内置标量类型

:-	-
Int	有符号 32 位整数
Float	有符号双精度浮点值
String	UTF-8 字符序列
Boolean	对或错布尔值类型
ID	唯一标识符

类型定义

:-	-
scalar	标量类型
type	对象类型
interface	接口类型
union	联合类型
enum	枚举类型
input	输入对象类型

类型修饰符

:-	-
String	可空字符串
String!	非空字符串
[String]	可空字符串列表
[String]!	可空字符串的非空列表
[String!]!	非空字符串的非空列表

输入参数

基本输入

type Query {
  users(limit: Int): [User]
}

输入默认值

type Query {
  users(limit: Int = 10): [User]
}

具有多个参数的输入

type Query {
  users(limit: Int, sort: String): [User]
}

具有多个参数和默认值的输入

type Query {
  users(limit: Int = 10, sort: String): [User]
}
type Query {
  users(limit: Int, sort: String = "asc"): [User]
}
type Query {
  users(limit: Int = 10, sort: String = "asc"): [User]
}

输入类型

input ListUsersInput {
  limit: Int
  since_id: ID
}

type Mutation {
  users(params: ListUsersInput): [User]!
}

自定义标量

scalar Url
type User {
  name: String
  homepage: Url
}

接口

interface Foo {
  is_foo: Boolean
}
interface Goo {
  is_goo: Boolean
}
type Bar implements Foo {
  is_foo: Boolean
  is_bar: Boolean
}
type Baz implements Foo, Goo {
  is_foo: Boolean
  is_goo: Boolean
  is_baz: Boolean
}

实现一个或多个接口的对象

联合

type Foo {
  name: String
}
type Bar {
  is_bar: String
}
union SingleUnion = Foo
union MultipleUnion = Foo | Bar
type Root {
  single: SingleUnion
  multiple: MultipleUnion
}

一个或多个对象的联合

枚举

enum USER_STATE {
  NOT_FOUND
  ACTIVE
  INACTIVE
  SUSPENDED
}
type Root {
  stateForUser(userID: ID!): USER_STATE!
  users(state: USER_STATE, limit: Int = 10): [User]
}

查询和变更(Mutations)

字段

{
  hero {
    name
  }
}

结果:

{
  "data": {
    "hero": {
      "name": "R2-D2"
    }
  }
}

查询可以有注释

{
  hero {
    name
    # 查询可以有注释！
    friends {
      name
    }
  }
}

结果:

{
  "data": {
    "hero": {
      "name": "R2-D2",
      "friends": [
        { "name": "Luke Skywalker" },
        { "name": "Han Solo" }
      ]
    }
  }
}

参数 Arguments

{
  human(id: "1000") {
    name
    height
  }
}

结果:

{
  "data": {
    "human": {
      "name": "Luke Skywalker",
      "height": 1.72
    }
  }
}

不同类型的参数

{
  human(id: "1000") {
    name
    height(unit: FOOT)
  }
}

结果:

{
  "data": {
    "human": {
      "name": "Luke Skywalker",
      "height": 5.6430448
    }
  }
}

别名(Aliases)

{
  empireHero: hero(episode: EMPIRE) {
    name
  }
  jediHero: hero(episode: JEDI) {
    name
  }
}

结果:

{
  "data": {
    "empireHero": {
      "name": "Luke Skywalker"
    },
    "jediHero": {
      "name": "R2-D2"
    }
  }
}

片段(Fragments)

{
  leftComparison: hero(episode: EMPIRE) {
    ...comparisonFields
  }
  rightComparison: hero(episode: JEDI) {
    ...comparisonFields
  }
}
​
fragment comparisonFields on Character {
  name
  appearsIn
  friends {
    name
  }
}

结果:

{
  "data": {
    "leftComparison": {
      "name": "Luke Skywalker",
      "appearsIn": [
        "NEWHOPE",
        "EMPIRE",
        "JEDI"
      ],
      "friends": [
        { "name": "Han Solo" },
        { "name": "Leia Organa" },
        { "name": "C-3PO" },
        { "name": "R2-D2" }
      ]
    },
    "rightComparison": {
      "name": "R2-D2",
      "appearsIn": [
        "NEWHOPE",
        "EMPIRE",
        "JEDI"
      ],
      "friends": [
        { "name": "Luke Skywalker" },
        { "name": "Han Solo" },
        { "name": "Leia Organa" }
      ]
    }
  }
}

在片段内使用变量

query HeroComparison($first: Int = 3) {
  leftComparison: hero(episode: EMPIRE) {
    ...comparisonFields
  }
  rightComparison: hero(episode: JEDI) {
    ...comparisonFields
  }
}
​
fragment comparisonFields on Character {
  name
  friendsConnection(first: $first) {
    totalCount
    edges {
      node {
        name
      }
    }
  }
}

结果:

{
  "data": {
    "leftComparison": {
      "name": "Luke Skywalker",
      "friendsConnection": {
        "totalCount": 4,
        "edges": [
          {
            "node": {
              "name": "Han Solo"
            }
          },
          {
            "node": {
              "name": "Leia Organa"
            }
          }
        ]
      }
    },
    "rightComparison": {
      "name": "R2-D2",
      "friendsConnection": {
        "totalCount": 3,
        "edges": [
          {
            "node": {
              "name": "Luke Skywalker"
            }
          },
          {
            "node": {
              "name": "Han Solo"
            }
          }
        ]
      }
    }
  }
}

操作名称(Operation name)

query HeroNameAndFriends {
  hero {
    name
    friends {
      name
    }
  }
}

结果:

{
  "data": {
    "hero": {
      "name": "R2-D2",
      "friends": [
        { "name": "Luke Skywalker" },
        { "name": "Han Solo" },
        { "name": "Leia Organa" }
      ]
    }
  }
}

变量(Variables)

# { "graphiql": true, "variables": { "episode": JEDI } }
query HeroNameAndFriends($episode: Episode) {
  hero(episode: $episode) {
    name
    friends {
      name
    }
  }
}

变量前缀必须为 $，后跟其类型

默认变量(Default variables)

query HeroNameAndFriends($episode: Episode = "JEDI") {
  hero(episode: $episode) {
    name
    friends {
      name
    }
  }
}

指令(Directives)

query Hero($episode: Episode, $withFriends: Boolean!) {
  hero(episode: $episode) {
    name
    friends @include(if: $withFriends) {
      name
    }
  }
}

---

{ "episode": "JEDI", "withFriends": false }

结果:

{
  "data": { "hero": { "name": "R2-D2" } }
}

• @include(if: Boolean) 仅在参数为 true 时，包含此字段
• @skip(if: Boolean) 如果参数为 true，跳过此字段

变更(Mutations)

mutation CreateReviewForEpisode($ep: Episode!, $review: ReviewInput!) {
  createReview(episode: $ep, review: $review) {
    stars
    commentary
  }
}

---

{
  "ep": "JEDI",
  "review": {
    "stars": 5,
    "commentary": "This is a great movie!"
  }
}

结果:

{
  "data": {
    "createReview": {
      "stars": 5,
      "commentary": "This is a great movie!"
    }
  }
}

内联片段(Inline Fragments)

query HeroForEpisode($ep: Episode!) {
  hero(episode: $ep) {
    name
    ... on Droid {
      primaryFunction
    }
    ... on Human {
      height
    }
  }
}

---

{ "ep": "JEDI" }

结果:

{
  "data": {
    "hero": {
      "name": "R2-D2",
      "primaryFunction": "Astromech"
    }
  }
}

元字段(Meta fields)

{
  search(text: "an") {
    __typename
    ... on Human {
      name
    }
    ... on Droid {
      name
    }
    ... on Starship {
      name
    }
  }
}

结果:

{
  "data": {
    "search": [
      {
        "__typename": "Human",
        "name": "Han Solo"
      },
      {
        "__typename": "Human",
        "name": "Leia Organa"
      },
      {
        "__typename": "Starship",
        "name": "TIE Advanced x1"
      }
    ]
  }
}