GraphQL 渐进学习 02-GraphQL-组件构成知识整理
目标
- 对 GraphQL 构成的组件进行知识精要整理
- 组件构成有 5 个方面
- 查询变更 queries
- Schema 和类型 schema
- 验证 validation
- 执行 execution
- 内省 introspection
方便日后当手册查阅
代码
融合上述特性写了个代码,方便记忆
查询变更 queries
查询变更都是客户端代码
字段(Fields)
{
authors {
id
firstName
lastName
}
}
参数(Arguments)
{
author(id: 1) {
id
firstName
lastName
}
}
别名(Aliases)
{
author(id: 1) {
id
name: firstName
lastName
}
}
片段(Fragments)
{
author(id: 1) {
...authorFields
}
}
fragment authorFields on Author {
id
firstName
lastName
posts {
title
}
}
操作名称(Operation name)
query findAuthors {
authors {
id
firstName
lastName
posts {
title
}
}
}
变量(Variables)
输入
# query
query findAuthor($id: Int!) {
author(id: $id) {
id
firstName
lastName
posts {
title
}
}
}
# variables
{
"id": 1
}
输出
默认变量(Default variables)
query findAuthor($id: Int = 2) {
author(id: $id) {
id
firstName
lastName
posts {
title
}
}
}
指令(Directives)
# query
query findAuthor($id: Int = 1, $withPosts: Boolean!) {
author(id: $id) {
id
firstName
lastName
posts @include(if: $withPosts) {
title
}
}
}
# variables
{
"withPosts": false
}
@include(if: Boolean)
仅在参数为true
时,包含此字段。@skip(if: Boolean)
如果参数为true
时,跳过此字段。
变更(Mutations)
# query
mutation upPost($id: Int!) {
upvotePost(postId: $id) {
id
title
votes
}
}
# variables
{
"id": 1
}
变更中的多个字段(Multiple fields in mutations)
# query
mutation upPost($id: Int!) {
upVotePost(postId: $id) {
id
title
votes
}
clearVotePost(postId: $id) {
id
title
votes
}
}
# variables
{
"id": 1
}
# output
{
"data": {
"upVotePost": {
"id": 1,
"title": "Introduction to GraphQL",
"votes": 1
},
"clearVotePost": {
"id": 1,
"title": "Introduction to GraphQL",
"votes": 0
}
}
}
- 多个变更,按顺序先后执行,但是查询是并行的
内联片段(Inline Fragments)
query HeroForEpisode($ep: Episode!) {
hero(episode: $ep) {
name
... on Droid {
primaryFunction
}
... on Human {
height
}
}
}
元字段(Meta fields)
{
authors {
__typename
id
firstName
lastName
}
}
__typename
显示类型名称其它元字段,用于描述
内省
系统
Schema 和类型 schema
schema 定义是服务端代码
对象类型和字段(Object Types and Fields)
type Author {
"""
流水编号
"""
id: Int!
firstName: String
lastName: String
"""
用户发布的文章
"""
posts: [Post]
}
type
定义对象"""
标记注释Int
String
系统对象!
不能为空[
...]
数组String!
字符串不为空[String]!
数组不为空
默认标量类型
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
true 或者 falseID
ID 标量类型表示一个唯一标识符,通常用以重新获取对象或者作为缓存中的键。ID 类型使用和 String 一样的方式序列化;然而将其定义为 ID 意味着并不需要可读型。
自定义类型 scalar
scalar Date
详细请移步 03-GraphQL-scalar-自定义类型
枚举类型(Enumeration Types)
enum Country {
CN
ENG
JP
UK
CA
}
type Author {
"""
流水编号
"""
id: Int!
firstName: String
lastName: String
state(state: Country = CN): String
"""
the list of Posts by this author
"""
posts: [Post]
}
-
state
字段指定了枚举类型,默认值CN
接口(Interfaces)
interface Message {
content: String
}
type Notice implements Message {
content: String
noticeTime: Date
}
type Remind implements Message {
content: String
endTime: Date
}
联合类型(Union Types)
union MessageResult = Notice | Remind
输入类型(Input Types)
# 定义输入类型 `AuthorInput`
input AuthorInput {
firstName: String
lastName: String
state: String
}
# 指定变更变量类型
type Mutation {
addAuthor (
author: AuthorInput!
): Author
}
验证 validation
通过使用类型系统,你可以预判一个查询是否有效。这让服务器和客户端可以在无效查询创建时就有效地通知开发者,而不用依赖运行时检查。
执行 execution
一个 GraphQL 查询在被验证后,GraphQL 服务器会将之执行,并返回与请求的结构相对应的结果,该结果通常会是 JSON 的格式。
Query: {
human(obj, args, context) {
return context.db.loadHumanByID(args.id).then(
userData => new Human(userData)
)
}
}
obj
上一级对象,如果字段属于根节点查询类型通常不会被使用。args
可以提供在 GraphQL 查询中传入的参数。context
会被提供给所有解析器,并且持有重要的上下文信息比如当前登入的用户或者数据库访问对象。
内省 introspection
__schema
查询哪些对象可用
# 查询
{
__schema {
types {
name
kind
}
}
}
# 输出
{
"data": {
"__schema": {
"types": [
{
"name": "Query",
"kind": "OBJECT"
},
{
"name": "Post",
"kind": "OBJECT"
},
{
"name": "Int",
"kind": "SCALAR"
},
{
"name": "String",
"kind": "SCALAR"
},
{
"name": "Author",
"kind": "OBJECT"
},
{
"name": "Country",
"kind": "ENUM"
},
{
"name": "Message",
"kind": "INTERFACE"
},
{
"name": "MessageResult",
"kind": "UNION"
},
{
"name": "Notice",
"kind": "OBJECT"
},
{
"name": "Date",
"kind": "SCALAR"
},
{
"name": "Remind",
"kind": "OBJECT"
},
{
"name": "Mutation",
"kind": "OBJECT"
},
{
"name": "AuthorInput",
"kind": "INPUT_OBJECT"
},
{
"name": "__Schema",
"kind": "OBJECT"
},
{
"name": "__Type",
"kind": "OBJECT"
},
{
"name": "__TypeKind",
"kind": "ENUM"
},
{
"name": "Boolean",
"kind": "SCALAR"
},
{
"name": "__Field",
"kind": "OBJECT"
},
{
"name": "__InputValue",
"kind": "OBJECT"
},
{
"name": "__EnumValue",
"kind": "OBJECT"
},
{
"name": "__Directive",
"kind": "OBJECT"
},
{
"name": "__DirectiveLocation",
"kind": "ENUM"
}
]
}
}
}
- __Schema, __Type, __TypeKind, __Field, __InputValue, __EnumValue, __Directive - 这些有着两个下划线的类型是内省系统的一部分
queryType
查询对象名称
# 查询
{
__schema {
queryType {
name
}
}
}
# 输出
{
"data": {
"__schema": {
"queryType": {
"name": "Query"
}
}
}
}
__type
查询对象
# 查询
{
__type(name: "Notice") {
name
kind
description
fields {
name
type {
name
}
description
}
interfaces {
name
description
}
}
}
# 输出
{
"data": {
"__type": {
"name": "Notice",
"kind": "OBJECT",
"description": "通知对象",
"fields": [
{
"name": "content",
"type": {
"name": "String"
},
"description": "通知内容"
},
{
"name": "noticeTime",
"type": {
"name": "Date"
},
"description": "通知时间"
}
],
"interfaces": [
{
"name": "Message",
"description": "消息接口"
}
]
}
}
}
所有的查询对象
# 查询
{
__type(name: "Query") {
name
kind
fields {
name
description
args {
name
description
defaultValue
}
}
}
}
# 输出
{
"data": {
"__type": {
"name": "Query",
"kind": "OBJECT",
"fields": [
{
"name": "posts",
"description": "所有文章",
"args": []
},
{
"name": "authors",
"description": "所有作者",
"args": []
},
{
"name": "author",
"description": "",
"args": [
{
"name": "id",
"description": "作者ID",
"defaultValue": null
}
]
},
{
"name": "searchInterface",
"description": "",
"args": [
{
"name": "text",
"description": "",
"defaultValue": null
}
]
},
{
"name": "searchUnion",
"description": "",
"args": [
{
"name": "text",
"description": "",
"defaultValue": null
}
]
}
]
}
}
}