Is it possible to take an excerpt from the first rich text area in a matrix?

Question

I have blog articles set up on the site i'm working on to be built using a matrix, much the same way as in the features video about the matrix field. So it is entirely possible for an article to start with an image or a video.

What i'd like to be able to do is find the first text entry in the matrix and pull the first 155 characters out of it, creating an excerpt. The point of this is to pass that into a meta og:description tag (and i guess meta description too!)

Is it possible to do that with matrix content?

Answer 1

You can filter by block type: http://buildwithcraft.com/docs/matrix-fields#filtering-by-block-type

In short:

{% set ogDescription = false %}

{% for block in entry.myMatrixField.type('richText').limit(1) %}
  {% set ogDescription = block.text | striptags | slice(0, 155) %}
{% endfor %}

{% if ogDescription %}
  ...
{% endif %}

Also, this was suggested in the comments:

{{ entry.myMatrixField.type('richText').first() | striptags | slice(0, 155) }}

Answer 2

We've designed Sprout SEO to help you handle situations like these. Personally, I think it's the easiest path to take for dealing with this situation. So, my first answer would be to consider using it.

There is an example on how to assign meta values in included Matrix blocks in the Sprout SEO docs here Extending a Base Layout

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But, this is a question on StackExchange so that answer alone is unsatisfying. If you'd like to dig into solving this issue yourself, to start, I'd recommend you try to get the best understanding you can of the Twig Processing Order. While part of the challenge your facing is how to grab the specific text you need from the field variable (Bill Chriswell's answer addresses that), another part of it may be where your variable exists in your templates.

For example, if you are managing your variables in a parent _layout template and trying to assign your excerpt within a block tag extending it, you're description variable is getting set after you are outputting your meta variables.

So, however you are assigning your meta variables you need to make sure that you are assigning the description variable in a way that it gets updated before you are actually outputting the meta values in your header.

I'll quote a couple paragraphs from the Twig Processing Order article linked above:

[T]he Twig processing order flows down the page. Variables are processed and become available farther down the page to be output. Sometimes however, we can only determine a value farther down the page, and the value itself needs to be output higher on the page.

Out of the box, some scenarios like this can be handled by Twig but things can get messy quick, and code that once felt dry can begin to feel harder to maintain. Other scenarios simply can't be solved without extending Twig or managing your variable with the help of a plugin.

Here are three methods mentioned in the article to consider if you want to get around this:

1. Try to set your variables as high on the page as you can. Even arrays of data can be queried and set as variables higher on the page. Once a variable exists, it's much easier to refer to that variable anywhere below it's first instance in your templates.
2. Create your page variables in a plugin. Craft allows you to set up routes to point to a Controller action instead of a page template.
3. Consider building a plugin and and managing the variable of the content you need access to in a Twig Global or public variable in the service layer of your plugin.