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通過(guò)Graphene，你可以快速構(gòu)建出一個(gè)支持按需查詢(xún)、實(shí)時(shí)更新的API服務(wù)。我們開(kāi)始這段有趣的學(xué)習(xí)之旅吧！

1. 快速入門(mén)

先安裝Graphene：

pip install graphene

小貼士：如果你計(jì)劃與Django一起使用，可以安裝 graphene-django。

2. 定義你的第一個(gè)Schema

在GraphQL中，Schema定義了API的類(lèi)型系統(tǒng)。我們創(chuàng)建一個(gè)簡(jiǎn)單的圖書(shū)管理系統(tǒng)：

import graphene



class Author(graphene.ObjectType):

    """作者信息"""

    name = graphene.String(description="作者姓名")

    books = graphene.List(lambda: Book, description="作者的作品")



class Book(graphene.ObjectType):

    """書(shū)籍信息"""

    title = graphene.String(description="書(shū)籍標(biāo)題")

    author = graphene.Field(Author, description="作者")

    pages = graphene.Int(description="頁(yè)數(shù)")

    price = graphene.Float(description="價(jià)格")



# 創(chuàng)建查詢(xún)

class Query(graphene.ObjectType):

    books = graphene.List(Book, description="所有書(shū)籍")

    author = graphene.Field(

        Author,

        name=graphene.String(required=True),

        description="根據(jù)姓名查詢(xún)作者"

    )



    def resolve_books(self, info):

        """獲取所有書(shū)籍"""

        return get_books()  # 實(shí)際項(xiàng)目中從數(shù)據(jù)庫(kù)獲取



    def resolve_author(self, info, name):

        """根據(jù)姓名查詢(xún)作者"""

        return get_author_by_name(name)  # 實(shí)際項(xiàng)目中從數(shù)據(jù)庫(kù)獲取



schema = graphene.Schema(query=Query)

一句話總結(jié)：Schema是GraphQL API的骨架，定義了可查詢(xún)的數(shù)據(jù)結(jié)構(gòu)和類(lèi)型。

3. 添加修改操作（Mutations）

class CreateBook(graphene.Mutation):

    """創(chuàng)建新書(shū)籍"""

    class Arguments:

        title = graphene.String(required=True)

        author_name = graphene.String(required=True)

        pages = graphene.Int()

        price = graphene.Float()



    book = graphene.Field(Book)



    def mutate(self, info, title, author_name, pages=None, price=None):

        author = get_or_create_author(author_name)

        book = create_book(title=title, author=author, pages=pages, price=price)

        return CreateBook(book=book)



class Mutation(graphene.ObjectType):

    create_book = CreateBook.Field()



# 更新schema

schema = graphene.Schema(query=Query, mutation=Mutation)

注意事項(xiàng)：

所有的修改操作都應(yīng)該通過(guò)Mutation實(shí)現(xiàn)
記得做好輸入驗(yàn)證和錯(cuò)誤處理

4. 集成到Web框架

以Flask為例，讓我們創(chuàng)建一個(gè)GraphQL endpoint：

from flask import Flask

from flask_graphql import GraphQLView



app = Flask(__name__)



app.add_url_rule(

    '/graphql',

    view_func=GraphQLView.as_view(

        'graphql',

        schema=schema,

        graphiql=True  # 啟用GraphiQL界面

    )

)



if __name__ == '__main__':

    app.run(debug=True)

小貼士：GraphiQL是一個(gè)超好用的調(diào)試工具，可以直接在瀏覽器中測(cè)試查詢(xún)。

5. 高級(jí)特性

接口和聯(lián)合類(lèi)型

class SearchResult(graphene.Union):

    """搜索結(jié)果可能是書(shū)籍或作者"""

    class Meta:

        types = (Book, Author)



class Node(graphene.Interface):

    """可查詢(xún)節(jié)點(diǎn)的接口"""

    id = graphene.ID(required=True)



class Book(graphene.ObjectType):

    class Meta:

        interfaces = (Node,)

數(shù)據(jù)加載優(yōu)化

from promise import Promise

from promise.dataloader import DataLoader



class AuthorLoader(DataLoader):

    def batch_load_fn(self, keys):

        authors = get_authors_by_ids(keys)  # 批量查詢(xún)作者

        return Promise.resolve([

            next((a for a in authors if a.id == key), None)

            for key in keys

        ])



# 在resolve方法中使用

def resolve_author(self, info):

    return info.context.author_loader.load(self.author_id)