GraphQL & Relay －串起前後端世界的橋樑

! # @zetavg 
fb.me/pokaichang72
串串起前後端資料的橋樑 
GraphQL  
& Relay

Q: 這個 app 需要多少 API
Endpoints?

Ans: 4
GET /api/todos.json
POST /api/todos.json
PATCH /api/todos/id.json
DELETE /api/todos/id.json

Q: 那這個 app 需要多少 API
Endpoints 呢?

/api/v1/posts.json
/api/v2/posts.json
/api/v3/posts.json
/api/v4/posts.json
/api/v65535/posts.json
⋯⋯

/api/posts.json
/api/posts.json?include=author
/api/posts.json?include=author,comments
/api/posts.json?cover=true&include=author,comments
/api/posts.json?cover=true&include=author,comments_with

$
{
"name": "Neson",
"bio":"Yet another geek.",
"followers": [◌, ◌, ◌],
"repos": [◌, ◌, ◌] 
}
$
{
"name": "Lucy",
"bio":"...",
"followers": [◌],
"repos": [◌, ◌] 
}
$
{
"name": "Ja
"bio":"..."
"followers"
"repos": [◌
}
$
{
"name": "Pusheen",
"bio":"Nyan nyan nyan~",
"followers": [◌],
"repos": [◌] 
}
!
{
"name": "Thing Compiler",
"description": "...",
"stargazers": [◌, ◌, ◌] 
}
!
{
"name": "Hello World",
"stargazers": [◌, ◌] 
}
!
{
"name": "Handy Ut
"description": ".
"stargazers": [◌]
}
!
{
"name": "Awes
"description"
"stargazers":
}
!
{
"name": "Todo",
"stargazers": [◌] 
}
!
{ }
{
"viewer": ◌ 
}
GraphQL

$
{
"name": "Neson",
"followers": [◌, ◌, ◌],
"repos": [◌, ◌, ◌] 
}
$
{
"name": "Lucy",
"bio":"...",
"followers": [◌],
"repos": [◌, ◌] 
}
$
{
"name": "Ja
"bio":"..."
"followers"
"repos": [◌
}
$
{
"name": "Pusheen",
"followers": [◌],
"repos": [◌] 
}
!
{
}
!
{
"name": "Hello World",
"stargazers": [◌, ◌] 
}
!
{
"name": "Handy Ut
"description": ".
"stargazers": [◌]
}
!
{
"name": "Awes
"description"
"stargazers":
}
!
{
"name": "Todo",
}
!
{ }
{
"viewer": ◌ 
}

$
{
"name": "Pusheen",
"followers": [◌],
"repos": [◌] 
}
$
{
"name"
"bio":
"follo
"repos
}
!
!
{
"name": "Todo",
}
!
{
}
!
{
"name": "Thi
"description
"stargazers"
}
!
{ }
{
"viewer": ◌ 
}
$
{
"name": "Neson",
"followers": [◌, ◌, ◌],
"repos": [◌, ◌, ◌] 
}
$ dd
dd
dd
dd

!
{
}
!
{
"name": "Thi
"description
"stargazers"
}
!
!
!
{
"name": "Todo",
}
{ }
{
"viewer": ◌ 
}
$
{
"name": "Neson",
"followers": [◌, ◌, ◌],
"repos": [◌, ◌, ◌] 
}
$
{
"name"
"bio":
"follo
"repos
}
$
{
"name": "Pusheen",
"followers": [◌],
"repos": [◌] 
}
$
$
$
$
$
$

!
!
{
"name": "Thi
"description
"stargazers"
}
$
{
"name": "Pusheen",
"followers": [◌],
"repos": [◌] 
}
!
!
{
"name": "Todo",
}
!
{
}
{ }
{
"viewer": ◌ 
}
$ $ $
$ $ $
$ $ $
$ $
/
$
{
"name"
"bio":
"follo
"repos
}
$
{
"name": "Neson",
"followers": [◌, ◌, ◌],
"repos": [◌, ◌, ◌] 
}

⬡ GraphQL 簡介
⬡ Relay ⼿手感評測
⬡ Relay 基本使⽤用
⬡ 全端案例例：GraphQL & Relay on Rails 
https://github.com/zetavg/RailsRelayTodoMVC
不會講到跟 Apollo 的比較
Outline

基本查詢
⬢ 最外層⼀一定是 query
⬢ 問什什麼得什什麼
{
"data": {
"viewer": {
"name": "Pokai Chang"
}
}
}
query {
viewer {
name
}
}

查詢更更多
⬢ 巢狀狀選取欄欄位 (ﬁeld)
{
"data": {
"viewer": {
"name": "Pokai Chang",
"birthday": {
"month": 7,
"day": 2
}
}
}
}
query {
viewer {
name
birthday {
month
day
}
}
}

巢狀狀查更更多
⬢ 底下的資料 (node) 可能是同⼀一種類型 (type)
{
"data": {
"viewer": {
"following": [
{ "name": "..." },
{ "name": "..." },
{ "name": "..." }
]
}
}
}
query {
viewer {
name
following {
name
}
}
}

巢狀狀查更更多多多多
⬢ 可以幹奇怪的事⋯⋯
{
"data": {
"viewer": {
"following": [
{
"name": "…",
"followers": [
{
"following": [
{
"name": "…",
"followers": [
{
"name": "Pokai C
query {
viewer {
name
following {
name
followers {
following {
name
followers {
name
}
}
}
}
}
}

型別定義即⽂文件
query {
viewer {
name
birthday {
month
day
}
following {
name
}
}
}
type Query {
viewer: User
}
type User {
name: String
birthday: Date
followers: [User]
following: [User]
}
type Date {
year: Integer
month: Integer
day: Integer
}

$
{
"name"
"bio":
"follo
"repos
}
$
{
"name": "Pusheen",
"followers": [◌],
"repos": [◌] 
}
!
{
}
!
{
"name": "Thi
"description
"stargazers"
}
!
!
!
{
"name": "Todo",
}
{ }
{
"viewer": ◌ 
}
$
{
"name": "Neson",
"followers": [◌, ◌, ◌],
"repos": [◌, ◌, ◌] 
}
query {
viewer {
name
bio
}
}

!
{
}
!
{
"name": "Thi
"description
"stargazers"
}
!
!
!
{
"name": "Todo",
}
{ }
{
"viewer": ◌ 
}
$
{
"name": "Neson",
"followers": [◌, ◌, ◌],
"repos": [◌, ◌, ◌] 
}
$
{
"name"
"bio":
"follo
"repos
}
$
{
"name": "Pusheen",
"followers": [◌],
"repos": [◌] 
}
query {
viewer {
name
bio
followers {
name
}
}
}

!
!
{
"name": "Todo",
}
$
{
"name"
"bio":
"follo
"repos
}
$
{
"name": "Pusheen",
"followers": [◌],
"repos": [◌] 
}
!
{
}
!
{
"name": "Thi
"description
"stargazers"
}
!
{ }
{
"viewer": ◌ 
}
$
{
"name": "Neson",
"followers": [◌, ◌, ◌],
"repos": [◌, ◌, ◌] 
}
query {
viewer {
name
bio
followers {
name
}
repos {
name
stargazers {
name
}
}
}
}

{ }
{
"viewer": ◌ 
}
!
!
{
"name": "Todo",
}
$
{
"name": "Neson",
"followers": [◌, ◌, ◌],
"repos": [◌, ◌, ◌] 
}
$
{
"name"
"bio":
"follo
"repos
}
$
{
"name": "Pusheen",
"followers": [◌],
"repos": [◌] 
}
!
{
}
!
{
"name": "Thi
"description
"stargazers"
}
!
query {
viewer {
name
bio
followers {
name
}
repos {
name
stargazers {
name
}
}
girlfriend {
name
}
}
}
'

query {
viewer {
name
bio
followers {
name
}
repos {
name
stargazers {
name
}
}
girlfriend {
name
}
}
}
{
"errors": [
{
"message": "Field 'girlfriend' doesn't 
exist on type ‘User’",
...
}
]
}
'

Arguments 參參數
⬢ 每個 ﬁeld 會定義可⽤用的參參數
query {
user(id: 1) {
name
}
}

Arguments 參參數
⬢ 也可以做巢狀狀查詢
query {
user(id: 1) {
name
repo(name: "awesome-graphql") {
name
description
}
}
}

Fragment 片段
fragment profileFields on User {
name
bio
avatarUrl
}
query {
viewer {
...profileFields
}
user(id: 1) {
...profileFields
}
}
先把固定會⽤用到的欄欄位
存成有意義的片段

改資料 ? Mutation
⬢ query 改成 mutation，data 放在 arguments
⬢ 其實就像 HTTP GET/POST，只是慣例例，沒有硬性限制
mutation {
addComment(input: { subjectId: 1, body: "Hi." }) {
subject {
comments {
body
}
}
}
}

無限捲軸
Caching
Prefetch Caching
Server Data Updating
Optimistic Update
Realtime Update

Relay 
 
Relay Modern
(Relay 1.0)

Redux 資料流
View
State
subscribe
Redux Store

Redux 資料流
View
State
Reducer
Action
subscribe
prevState

Redux 資料流
View
State
Reducer
Action
subscribe
prevState
Backend ?

Redux 資料流 ?
View
State
Reducer
Action
subscribe
prevState
Backend
Action
Action
Action

Redux 資料流 ?
View
Action
Action
Action
Action
Backend
State
State
State
Reducer
Reducer Reducer
Reducer
???
???

Relay 的狀狀況
View
$
$
$ $
$
dd
$ $ $ $
dd
dd
dd
Relay Store

Relay 的狀狀況
View
$
$ $
$
dd
$ $ $ $
dd
dd
dd
Relay Store
viewer {
name
bio
}
$
Backend
query {
viewer {
name
bio
}
}
{
"data": {
"viewer": {
"name": "…",
"Bio": "…"
}
}
}

Relay 的狀狀況
View
ㄎㄎㄎㄎ$
$ $
$
dd
$ $ $ $
dd
dd
dd
Relay Store
viewer {
name
bio
}
$

Relay 的狀狀況
View
ㄎㄎㄎㄎ
dd
dd
dd
dd
$ $
$ $ $ $ $
viewer {
name
bio
}
$
$
viewer {
followers {
name
}
}
Backend
query {
viewer {
followers {
name
}
}
}
{
"data": {
"viewer": {
"followers": […]
}
}
}
Relay Store
Request only the diﬀ!

Relay 的狀狀況
View
ㄎㄎㄎㄎ
dd
dd
dd
dd
$ $
$ $ $ $ $
viewer {
name
bio
}
$
$
viewer {
followers {
name
}
}

Relay 的狀狀況
viewer {
name
bio
}
View
$
ㄎㄎㄎㄎ$
$ $
$ $ $ $ $
viewer {
followers {
name
}
}
dd
dd
dd
dd
viewer {
repos {
name
description
}
}
Backend
query {
viewer {
repos {
name
description
}
}
}
{
"data": {
"viewer": {
"repos": […]
}
}
}

Relay 的狀狀況
viewer {
name
bio
}
View
$
ㄎㄎㄎㄎ$
$ $
$ $ $ $ $
viewer {
followers {
name
}
}
dd
dd
dd
dd
viewer {
repos {
name
description
}
}

Relay 的狀狀況
View
$
ㄎㄎㄎㄎ$
$ $
$ $ $ $ $
dd
dd
dd
dd
RenameRepoMutation(
repoID: "…",
name: ""
)

Relay 的狀狀況
View
$
ㄎㄎㄎㄎ$
$ $
$ $ $ $ $
dd
dd
dd
dd
RenameRepoMutation(
repoID: "…",
name: ""
)
Optimistic Updater

Relay 的狀狀況
View
$
ㄎㄎㄎㄎ$
$ $
$ $ $ $ $
dd
dd
dd
dd
RenameRepoMutation(
repoID: "…",
name: ""
)
Optimistic UpdaterBackend
Updater

想分⾴頁 ? Connections
⬢ 游標分⾴頁法：Relay Cursor Connections
query {
viewer {
friends(first: 10, after: "someCursor") {
edges {
cursor
node {
id
name
}
}
pageInfo {
hasNextPage
}
}
}
}
Edge (UserEdgeType)
Node (UserType)
{ … }
Cursor
游標 Connection
Edges
Edge (UserEdgeType)
Node (UserType)
{ … }
Cursor
Edge (UserEdgeTy
Node (UserType
{ … }
Cursor
Page Info
起始游標

⬢ Oﬀset based pagination
⬢ Cursor based pagination
Why Cursor?
page 1 page 2
page 1 page 2
page 3
page 3
' 壞ㄌ
next 5next 5

⬡ Relay 可信的 Optimistic Updater 機制可以做
「連線問題時重試」甚⾄至離線更更動上線後同步
⬡ Relay 的 backend 不⼀一定要是 server，也許可以
是裝置上的 database
⬡ 再狂⼀一點，也許我們還能透過⾃自⼰己實作 Relay
RecordSource 組出這樣的架構：
Fun Things to Try
RelayRelay ViewServer
Client DB Memory

適⽤用情況
⬢ Data driven，data 越多越雜，投資越划算
⬢ React app
⬢ 略略懂後端
⬢ 踩雷的勇氣
Relay Environment
Handler Provider
Network Layer
Store
Record Source
GraphQL Endpoint
Query Renderer
Container
Component
Fragment
Query

在 React 專案中安裝 Relay
$ yarn add react-relay

安裝 GraphQL 語法識別外掛
$ yarn add --dev babel-plugin-relay

記得⼿手動加 Babel Plugin
⬢ 編輯 .eslintrc 或 package.json
"plugins": [
"relay",
]

安裝 Relay GraphQL 編譯器
$ yarn add --dev relay-compiler

使⽤用 relay-compiler
⬢ 在 JavaScript 裡寫的 GraphQL 需要被事先編譯⋯⋯ 
 
⬢ 改了了 graphql`…` tag 裡⾯面的內容後都要跑⼀一次
⬢ 或是加上 --watch 參參數監看變化
$ relay-compiler --src ./src --schema ./schema.graphql
源碼⽬目錄 GraphQL Schema 檔位置

import { Environment } from ‘relay-runtime’
const environment = new Environment({
network,
store,
})
export default environment
環境準備
Relay Environment
Handler Provider
Network Layer
Store
Record Source
GraphQL Endpoint
Network Layer
Store
⬢ 先看整個環境⋯⋯

import { Network } from ‘relay-runtime'
const API_ENDPOINT = 'https://api.github.com/graphql'
const fetchQuery = (operation, variables) => {
return fetch(API_ENDPOINT, {
method: 'POST',
body: JSON.stringify({
query: operation.text,
variables,
}),
}).then(response => response.json())
}
const network = Network.create(fetchQuery)
exports default network
Relay 網路路層
⬢ 給⼀一個溝通介⾯面，⼀一般就是包裝 fetch
Relay Environment
Handler Provider
Network Layer
Store
Record Source
GraphQL Endpoint

import {
RecordSource,
Store,
} from 'relay-runtime'
const source = new RecordSource()
const store = new Store(source)
export default store
Relay 倉儲
Relay Environment
Handler Provider
Network Layer
Store
Record Source
GraphQL Endpoint
⬢ Relay 內建具備 garbage collection 的 in-memory
record source

以上，前置準備完成 🎉

const MyProfile = () => (
<QueryRenderer
environment={environment}
query={graphql`
query MyProfileQuery {
viewer {
name
}
}
`}
render={({ error, props }) => {
if (error) {
return <Text>{error.message}</Text>
} else if (props) {
return <Text>Hello, {props.viewer.name}!</Text>
}
return <Text>Loading...</Text>
}}
/>
)
基本招 QueryRenderer
可以設計載入中假畫⾯面
注意名字有規定⽤用 "[檔案名稱]Query"
Relay Environment
Handler Provider
Network Layer
Store
Record Source
GraphQL Endpoint
Query Renderer
Component
Query

const UserProfileComponent = ({ user }) => (
<Text>Hello, {user.name}!</Text>
)
const UserProfile = createFragmentContainer(
UserProfileComponent,
graphql`
fragment UserProfile_user on User {
name
login
avatarUrl
}
`,
)
export default UserProfile
拆元件 FragmentContainer
注意名字也有規定⽤用 "[檔案名稱]_[prop 名稱]"
Relay Environment
Store
Query Renderer
Container
Component
Fragment
Query

拆元件 FragmentContainer
直接引⽤用定義在 Container 裡的 Fragment
Relay Environment
Store
Query Renderer
Container
Component
Fragment
Query
import MyProfile from '...'
const MyProfile = () => (
<QueryRenderer
environment={environment}
query={graphql`
query MyProfileQuery {
viewer {
...UserProfile_user
}
}
`}
render={({ error, props }) => {
if (error) {
return <Text>{error.message}</Text>
} else if (props) {
return <MyProfile user={props.viewer} />
}
return <Text>Loading...</Text>
}}
/>
)

Component Tree 層層疊疊
Query Renderer
Container Fragment
Query
ContainerContainer
Component Component
FragmentFragment
const UserProfileComponent = ({ user }) => (
<View>
<UserName user={user} />
<UserBio user={user} />
</View>
)
const UserProfile = createFragmentContainer(
UserProfileComponent,
graphql`
fragment UserProfile_user on User {
...UserName_user
...UserBio_user
}
`,
)
const UserNameComponent = ({ user }) => (
<Text>Hello, {user.name}!</Text>
)
const UserName = createFragmentContainer(
UserNameComponent,
graphql`
fragment UserName_user on User {
name
avatarUrl
}
`,
)
const UserBioComponent = ({ user }) => (
<Text>{user.bio}</Text>
)
const UserBio = createFragmentContainer(
UserBioComponent,
graphql`
fragment UserBio_user on User {
bio
}
`,
)

特種 Container
⬢ RefetchContainer
⬡ 提供 instance method 可以改⽤用不同 arguments 索取資料
⬢ PaginationContainer
⬡ RefetchContainer 進化版
⬡ ⽤用 Relay Connection 做分⾴頁專⽤用
⬡ 可以做出 loadMore()、refresh() 等 method 給無限捲軸和
pull to refresh 使⽤用

Mutation
const mutation = graphql`
mutation AddCommentMutation(
$input: AddCommentInput!
) {
addComment(input: $input) {
clientMutationId
commentEdge {
cursor
node {
id
body
}
}
subject {
id
commentsCount
}
}
}
`
let variables = {
input: {
subjectId: "aGVsbG8=",
body: "Hello Relay",
}
}
commitMutation(
environment,
{
mutation,
variables,
onCompleted: (response) => {
console.log('Success!')
},
onError: (err) => {
console.error(err)
},
},
)
1
2
3
1
2
3
⼀一樣有命名規定
宣告 $input 變數以及型別，內容可以在使⽤用時再指定
與 query ⼀一樣列列出欄欄位，這裡需要列列出所有 mutation 執⾏行行後會變更更或新增的資料
2

⬢ 還有需要做的事⋯⋯
Mutation Updater
const mutation = graphql`
mutation AddCommentMutation(
$input: AddCommentInput!
) {
addComment(input: $input) {
clientMutationId
commentEdge {
cursor
node {
id
body
}
}
subject {
id
commentsCount
}
}
}
`
Mutation 執⾏行行後，我們需要把新的 edge 安插到 
某個 subject 底下的 comments connection
若若在 payload root 發現具有 id 的 node， 
Relay 慣例例會幫我們更更新好 store 中相應的 node

Mutation Updater
commitMutation(
environment,
{
mutation,
variables: { ... },
updater: (store) => {
const payload = store.getRootField('addComment')
const newEdge = payload.getLinkedRecord('commentEdge')
const subject = payload.getLinkedRecord('subject')
const conn =
ConnectionHandler.getConnection(subject, ‘commentsConnection')
ConnectionHandler.insertEdgeAfter(conn, newEdge)
},
optimisticUpdater: (store) => {
…
},
},
)
可⾃自訂 store 的 update ⽅方式

Mutation Updater
},
optimisticUpdater: (store) => {
const subject = store.get(subjectID)
const newCommentID = `client:newComment:${tempID++}`
const newNode = store.create(newCommentID, 'Comment')
newNode.setValue(newCommentID, 'id')
newNode.setValue(variables.input.body, 'body')
const newEdge = store.create(
`client:newCommentEdge:${tempID++}`,
'TodoItemEdge',
)
newEdge.setLinkedRecord(newNode, 'node')
const conn = ConnectionHandler.getConnection(subject, 'commentsConnection')
subject.setValue(
subject.getValue('commentsCount') + 1,
'commentsCount',
)
},
},
)
製作出暫時的 node
製作出暫時的 edge
把暫時的 edge 安插進 connection
⼿手動更更新計數器

(GraphQL + Relay) on Rails
全端⼀一天可以寫完，拿來來做 RN 更更顯神⼒力力

(GraphQL + Relay) on Rails
Debug 省下的時間可以拿來來調各種 1px

Image source: https://blog.codinghorror.com/learn-to-read-the-source-luke/
請⾒見見 https://github.com/zetavg/RailsRelayTodoMVC

GraphQL & Relay －串起前後端世界的橋樑

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