#Is there a way for a component to automatically access the props of a layout it’s part of?

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tidal pollen
#

I have a component that I want to display the current page’s title and some other info, which I can put wherever I want. Is there a way to do this without having to type in the title again?

strange pollenBOT
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Hi @tidal pollen. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:

#

Astro doesn’t provide a built‑in way for a child component to “automatically” see another component’s props just because it’s rendered inside that component.

Data flows one way: from parent to child via props, or via slots for child HTML content. [Component props; Slots]

So for your case:

  • Your layout receives the page title as a prop (e.g. const { title } = Astro.props;). [Layouts]
  • Any component that needs that title must have it passed explicitly as a prop from the layout:
---
// In your layout
import PageInfo from '../components/PageInfo.astro';
const { title } = Astro.props;
---
<html>
  <body>
    <PageInfo title={title} />
    <slot />
  </body>
</html>

---
// PageInfo.astro
const { title } = Astro.props;
---
<p>Current page: {title}</p>

If you need something globally available across a request (not just layout → child), Astro’s supported mechanism is locals via middleware, but that’s for request-level data, not layout props specifically. [Middleware locals; Astro.locals]

So: you do have to pass the title again as a prop (or move the “source of truth” for the title into locals or some shared place and have both layout and component read from there), but there’s no hidden automatic sharing of layout props.

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

#

@tidal pollen Kapa.ai is still learning and improving, please let me know how I did by reacting below.

tidal pollen
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@strange pollen I’m trying to do this within an mdx file. Is there a way to get MDX frontmatter data as a variable in the body?

strange pollenBOT
#

Let me check the knowledge base for you again. One moment! :books:

#

Yes. With Astro’s MDX integration you can use frontmatter values directly in the MDX body via a frontmatter object.

Example:

---
title: 'My first MDX post'
author: 'Houston'
---

{frontmatter.title}
Written by: {frontmatter.author}

Here frontmatter.title and frontmatter.author come from the MDX frontmatter and can be used anywhere in the body. [MDX frontmatter]

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

#

@tidal pollen Kapa.ai is still learning and improving, please let me know how I did by reacting below.

tidal pollen
#

@strange pollen I’m now trying to create a layout, and I’d like to add this component and have it use the frontmatter from the file that uses the layout. Is that possible?

strange pollenBOT
#

Let me check the knowledge base for you again. One moment! :books:

#

Yes, that’s exactly what Markdown/MDX layouts are for in Astro.

When you use the special layout frontmatter property in a Markdown/MDX file under src/pages/, Astro automatically passes that file’s frontmatter (and other data) into the layout via Astro.props.frontmatter. [Markdown layouts; Frontmatter layout property]

So you can:

  1. Define a layout that reads frontmatter:
---
// src/layouts/MarkdownPostLayout.astro
import PageInfo from '../components/PageInfo.astro';
const { frontmatter } = Astro.props;
---
<meta charset="utf-8" />
<PageInfo frontmatter={frontmatter} />
<h1>{frontmatter.title}</h1>
<slot />
  1. Use that layout from a Markdown/MDX file:
---
layout: ../../layouts/MarkdownPostLayout.astro
title: 'My First Blog Post'
author: 'Astro Learner'
pubDate: 2022-07-01
---
Post content here…
  1. In your component, consume the passed frontmatter (or just the fields you care about):
---
// src/components/PageInfo.astro
const { frontmatter } = Astro.props;
// or: const { title, author } = Astro.props;
---
<p>{frontmatter.title} — {frontmatter.author}</p>
#

Key point: the layout gets the page’s frontmatter automatically; your component can then receive that data as normal props from the layout. There’s no way for the component to “magically” read the layout’s props without them being passed, but you only define the frontmatter once in the MD/MDX file. [Markdown layout props; Tutorial example]

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

#

@tidal pollen Kapa.ai is still learning and improving, please let me know how I did by reacting below.

tidal pollen
#

@strange pollen can you remind me how Astro knows what layout to use if I don’t set it manually in the file? Is it that there’s always an outer layout, and when I set it manually it might add an inner layout?

strange pollenBOT
#

Let me check the knowledge base for you again. One moment! :books:

#

Astro only “auto-picks” a layout in one specific case: individual Markdown/MDX pages in src/pages/ that do not use the special layout frontmatter.

  • For a plain .md page in src/pages/, Astro will automatically wrap the rendered Markdown in a basic HTML document and add things like <meta charset="utf-8"> for you. [Individual Markdown pages]
  • If you add a layout frontmatter property, Astro stops using that default wrapper and instead uses the .astro layout component you specify. That layout is responsible for the full page shell (<html>, <head>, <body>, meta tags, etc.). [Markdown layouts; Frontmatter layout property]

There isn’t a hidden “outer layout” plus an “inner layout” chosen automatically. When you set layout: ../layouts/MyLayout.astro in frontmatter, that layout becomes the page shell. If you want multiple layers (e.g. MarkdownPostLayout inside BaseLayout), you explicitly nest them yourself in your layout component. [Nesting layouts; Nest your two layouts]

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

#

@tidal pollen Kapa.ai is still learning and improving, please let me know how I did by reacting below.

tidal pollen
#

@strange pollen Does it work to set a default layout using content.config.ts?

strange pollenBOT
#

Let me check the knowledge base for you again. One moment! :books:

#

I’m sorry, but the provided knowledge sources don’t mention any way to set a default layout via content.config.ts.

What they do say is:

  • The special layout frontmatter field is only recognized for Markdown/MDX files in src/pages/ using file-based routing, and is not a special field for content collections. [Markdown layouts; Frontmatter layout property]
  • For content collections, you query entries (e.g. with getCollection() and render()) and then wrap them in whatever layout you choose in your route component, e.g. src/pages/posts/[...slug].astro manually uses MarkdownPostLayout. [Generate pages]

There is no documented mechanism in these sources to declare a “default layout” for a collection in content.config.ts; layouts are chosen where you render the content (e.g. in your [...slug].astro page), not in the collection definition.

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: