将ImageSharp作为字段添加到MarkdownRemark节点(不是frontmatter)

问题描述

我要尝试使用以下graphQL查询:

I have the following graphQL query I'm trying to get working:

 {
      allMarkdownRemark(
        limit: 1000
      ) {
        edges {
          node {
            id
            parent {
              id
            }
            fields{
              slug
              hero {
                childImageSharp {
                  fixed {
                    src
                  }
                }
              }
            }
            frontmatter {
              template
            }
          }
        }
      }
    }

hero字段当前使用以下代码返回图像的路径:

The hero field currently returns a path to an image using the following code:

exports.onCreateNode = ({ node, actions, getNode }) => {
  const { createNodeField } = actions

  // Add slug to MarkdownRemark node
  if (node.internal.type === 'MarkdownRemark') {
    const value = createFilePath({ node, getNode, basePath: 'library' })
    const { dir } = getNode(node.parent)
    const getHero = (d) => {
      let hero = `${__dirname}/src/images/no-hero.gif`
      if (fs.existsSync(`${d}/hero.jpg`)) hero = `${d}/hero.jpg`
      if (fs.existsSync(`${d}/hero.png`)) hero = `${d}/hero.png`
      if (fs.existsSync(`${d}/hero.gif`)) hero = `${d}/hero.gif`
      return hero
    }
    createNodeField({
      node,
      name: 'slug',
      value,
    })

    createNodeField({
      node,
      name: 'hero',
      value: getHero(dir),
    })
  }
}

我已经看到其他人对frontmatter中的图像路径进行了类似的操作，但是我不想在很容易获得graphql来查看文件路径而不必指定它的情况下使用frontmatter .

I've seen other people do something similar with an image path in the frontmatter but I don't want to have to use the frontmatter when it's easy enough to get graphql to see the file path without having to specify it.

但是，当我尝试上述操作时，出现以下错误:

However when I try the above I get the following error:

有没有办法让我childImageSharp识别此字段?

Is there a way I can get childImageSharp to recognize this field?

推荐答案

我再次(希望)一劳永逸地解决此问题(请参阅我们的历史记录).

I'm back again to (hopefully) settle this issue once and for all (see our history here).

这一次，我们将英雄图像的ImageSharp附加到MarkdownRemark节点.您的方法正确，有1个警告:盖茨比似乎只能识别相对路径，即以点开头的路径.

This time, we'll attach the hero image's ImageSharp to the MarkdownRemark node. Your approach is correct, with 1 caveat: Gatsby seems to only recognize relative paths, i.e path starting with a dot.

您可以在代码中轻松解决此问题:

You can fix this easily in your code:

    const getHero = (d) => {
      let hero = `${__dirname}/src/images/no-hero.gif`

  -   if (fs.existsSync(`${d}/hero.jpg`)) hero = `${d}/hero.jpg`
  -   if (fs.existsSync(`${d}/hero.png`)) hero = `${d}/hero.png`
  -   if (fs.existsSync(`${d}/hero.gif`)) hero = `${d}/hero.gif`

  +   if (fs.existsSync(`${d}/hero.jpg`)) hero = `./hero.jpg`
  +   if (fs.existsSync(`${d}/hero.png`)) hero = `./hero.png`
  +   if (fs.existsSync(`${d}/hero.gif`)) hero = `./hero.gif`

      return hero
    }
    createNodeField({
      node,
      name: 'hero',
      value: getHero(dir),
    })

这应该可行，尽管我想提供另一种英雄搜索功能.我们可以使用fs.readdir来获取dir中的文件列表，然后找到名称为"hero"的文件:

This should work, though I want to provide an alternative hero search function. We can get a list of files in dir with fs.readdir, then find a file with the name 'hero':

exports.onCreateNode = async ({
  node, actions,
}) => {
  const { createNodeField } = actions

  if (node.internal.type === 'MarkdownRemark') {
    const { dir } = path.parse(node.fileAbsolutePath)

    const heroImage = await new Promise((res, rej) => {

      // get a list of files in `dir`
      fs.readdir(dir, (err, files) => {
        if (err) rej(err)

        // if there's a file named `hero`, return it
        res(files.find(file => file.includes('hero')))
      })
    })

    // path.relative will return a (surprise!) a relative path from arg 1 to arg 2.
    // you can use this to set up your default hero
    const heroPath = heroImage 
      ? `./${heroImage}` 
      : path.relative(dir, 'src/images/default-hero.jpg')

    // create a node with relative path
    createNodeField({
      node,
      name: 'hero',
      value: `./${heroImage}`,
    })
  }
}

这样，只要存在，我们就不会在乎英雄图像的扩展名是什么.我使用String.prototype.includes，但是为了安全起见，您可能想使用regex传递允许的扩展列表，例如/hero.(png|jpg|gif|svg)/. (我认为您的解决方案更具可读性，但我更喜欢每个节点仅访问一次文件系统.)

This way we don't care what the hero image's extension is, as long as it exists. I use String.prototype.includes, but you might want to use regex to pass in a list of allowed extensions, to be safe, like /hero.(png|jpg|gif|svg)/. (I think your solution is more readable, but I prefer to access the file system only once per node.)

您还可以使用 path.relative 查找默认路径的相对路径英雄形象.

You can also use path.relative to find the relative path to a default hero image.

现在，此graphql查询有效:

Now, this graphql query works:

但是，这种方法存在一个小问题:它破坏了graphql过滤器类型！当我尝试基于hero进行查询和过滤时，出现此错误:

However, there's a minor problem with this approach: it breaks graphql filter type! When I try to query and filter based on hero, I get this error:

也许盖茨比忘记了重新推断hero的类型，所以它仍然不是File，而是String.如果需要过滤器工作，这很烦人.

Perhaps Gatsby forgot to re-infer the type of hero, so instead of being a File, it is still a String. This is annoying if you need the filter to work.

这是一种解决方法:我们不会自己要求Gatsby链接文件，而是会自己处理.

Here's a workaround: Instead of asking Gatsby to link the file, we'll do it ourselves.

exports.onCreateNode = async ({
  node, actions, getNode, getNodesByType,
}) => {
  const { createNodeField } = actions

  // Add slug to MarkdownRemark node
  if (node.internal.type === 'MarkdownRemark') {
    const { dir } = path.parse(node.fileAbsolutePath)
    const heroImage = await new Promise((res, rej) => {
      fs.readdir(dir, (err, files) => {
        if (err) rej(err)
        res(files.find(file => file.includes('hero')))
      })
    })

    // substitute with a default image if there's no hero image
    const heroPath = heroImage ? path.join(dir, heroImage) : path.resolve(__dirname, 'src/images/default-hero.jpg')

    // get all file nodes
    const fileNodes = getNodesByType('File')

    // find the hero image's node
    const heroNode = fileNodes.find(fileNode => fileNode.absolutePath === heroPath)
    createNodeField({
      node,
      name: 'hero___NODE',
      value: heroNode.id,
    })
  }
}

现在我们可以再次过滤hero字段:

And now we can filter the hero field again:

如果您不需要按英雄图像过滤内容，则最好让gatsby处理节点类型.

If you don't need to filter content by hero image though, letting gatsby handle node type is much preferable.

让我知道您是否在尝试此操作时遇到问题.

Let me know if you run into issues trying this.

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