Gatsby - 在 gatsby-node.js 中添加带有参数的 GraphQL 查询

Question

在gatsby-node.js我有两个从Contentful 获取数据的查询。我想添加一个新查询，它根据特定内容的slug（Contentful 的内容模型中设置的字段）加载特定内容的数据。

这就是我所拥有的：

  return graphql(
    `
      {
        allContentfulBlogPost {
          edges {
            node {
              id
              slug
            }
          }
        }
        allContentfulCaseStudy(filter: { slug: { ne: "dummy-content" } }) {
          edges {
            node {
              id
              slug
            }
          }
        }
        contentfulCaseStudy(slug: { eq: $slug }) { // <=== Here is the problem
          title
          overview
        }
      }
    `
  )
    .then(result => {
      if (result.errors) {
        console.log("Error retrieving contentful data", result.errors)
      }
    })
    .catch(error => {
      console.log("Error retrieving contentful data", error)
    })
}

所以，我想查询在contentfulCaseStudy(slug: { eq: $slug }) 中传递slug 的特定案例研究，但它不起作用。当我启动npm run develop时它会抛出这个错误：

 ERROR #85901  GRAPHQL

There was an error in your GraphQL query:

Variable "$slug" is not defined.

File: gatsby-node.js:13:10

Error retrieving contentful data [
  GraphQLError: Variable "$slug" is not defined.
      at Object.leave (C:\Edited\edited\edited\edited\node_modules\graphql\validation\rules\NoUndefinedVariables.js:38:33)
      at Object.leave (C:\Edited\edited\edited\edited\node_modules\graphql\language\visitor.js:345:29)
      at Object.leave (C:\Edited\edited\edited\edited\node_modules\graphql\language\visitor.js:395:21)
      at visit (C:\Edited\edited\edited\edited\node_modules\graphql\language\visitor.js:242:26)
      at validate (C:\Edited\edited\edited\edited\node_modules\graphql\validation\validate.js:73:24)
      at GraphQLRunner.validate (C:\Edited\edited\edited\edited\node_modules\gatsby\dist\query\graphql-runner.js:79:44)
      at GraphQLRunner.query (C:\Edited\edited\edited\edited\node_modules\gatsby\dist\query\graphql-runner.js:144:25)
      at C:\Edited\edited\edited\edited\node_modules\gatsby\dist\bootstrap\create-graphql-runner.js:40:19
      at Object.exports.createPages (C:\Edited\edited\edited\edited\gatsby-node.js:13:10)
      at runAPI (C:\Edited\edited\edited\edited\node_modules\gatsby\dist\utils\api-runner-node.js:259:37)
      at Promise.catch.decorateEvent.pluginName (C:\Edited\edited\edited\edited\node_modules\gatsby\dist\utils\api-runner-node.js:378:15)
      at Promise._execute (C:\Edited\edited\edited\edited\node_modules\bluebird\js\release\debuggability.js:384:9)
      at Promise._resolveFromExecutor (C:\Edited\edited\edited\edited\node_modules\bluebird\js\release\promise.js:518:18)
      at new Promise (C:\Edited\edited\edited\edited\node_modules\bluebird\js\release\promise.js:103:10)
      at C:\Edited\edited\edited\edited\node_modules\gatsby\dist\utils\api-runner-node.js:377:12
      at tryCatcher (C:\Edited\edited\edited\edited\node_modules\bluebird\js\release\util.js:16:23) {
    locations: [ [Object], [Object] ]
  }

是否可以请求将 slug 作为参数传递的特定案例研究？如果是这样，它是如何完成的？

Answer 1

简短的回答是你不能直接。您可以使用硬编码参数进行过滤，而不是使用动态预查询值。

但是，您尝试对 $slug 执行的操作是通过 context API 传递变量。

您想要实现的流程是：

• 从allContentfulCaseStudy 的内容数据中获取和创建页面
• 使用contentfulCaseStudy 中的allContentfulCaseStudy 的slug 来过滤每个contentfulCaseStudy 的查询。

因此，您需要将您的contentfulCaseStudy 移动到您的template.js，修改您的gatsby-node.js，如下所示：

exports.createPages = async ({ graphql, actions, reporter }) => {
  const { createPage } = actions

  const result = await graphql(
    `
      {
        allContentfulCaseStudy(filter: { slug: { ne: "dummy-content" } }) {
          edges {
            node {
              id
              slug
            }
          }
        }
      }
    `
  )

  if (result.errors) {
    reporter.panicOnBuild(`Error while running GraphQL query.`)
    return
  }

  const caseStudyTemplate= path.resolve(`src/templates/case-study.js`)

  result.data.allContentfulCaseStudy.edges.forEach(({ node }) => {
    createPage({
      path,
      component: caseStudyTemplate,
      context: {
        slug: node.slug,
      },
    })
  })
}

现在，在您的case-study.js 中，您可以使用slug 变量，因为您通过context 在您的page query 中传递它。所以：

import React from "react"
import { graphql } from "gatsby"
import Layout from "../components/layout"

export default function CaseStudy({ data }) {
  const caseStudy= data.contentfulCaseStudy
  return (
    <Layout>
      <div>
        <h1>{caseStudy.title}</h1>
      </div>
    </Layout>
  )
}

export const query = graphql`
  query($slug: String!) {
        contentfulCaseStudy(slug: { eq: $slug }) {
          title
          overview
        }
  }
`

检查您的localhost:8000/___graphql Playground，看看嵌套的title 和overview 是否在contentfulCaseStudy 下，或者您是否需要修改查询结构。

进一步阅读：

• Creating Pages from Data Programmatically
• How to add query variables to a page query