Getting an asset Url from an entry loop into a meta tag I found it pretty straightforward to get something like dynamic page titles working by setting a variable at the template level and pulling that into my site's meta tags:
My _layout.twig:
&lt;head&gt;
{% if title is defined %}
&lt;title&gt;{{ title }}&lt;/title&gt;
{% endif %}
&lt;/head&gt;

My template.twig:
{% set title = entry.title %}

But what's the best practice for pulling something like an asset URL that needs queried from within {% block content %}? I'm running a for loop on my asset field to grab the Url from within the template, but this doesn't seem to work outside of {% block content %}, and if I run it from within {% block content %} the variable doesn't carry over to _layout.twig where I need it in the meta tag.
My _layout.twig looks like this:
{% if openGraphImage is defined %}
&lt;meta property=&quot;og:image&quot; content=&quot;{{openGraphImage}}&quot; /&gt;
{% endif %}

But how can I define an image Url that's coming from within an entry query and have it pass back to the meta tag?
I didn't have a full understanding of how blocks work, but I've solved my problem. I think because I was trying to set the variable in my template outside of the block (and I was trying to bring it into my _layout.twig file without referencing the block I was calling) nothing was getting properly passed from one file to the other. The solution I'm now using looks like this:
_layout.twig:
&lt;meta property=&quot;og:image&quot; content=&quot;{% block ogImage %}{% endblock %}&quot; /&gt;

template.twig:
{% block ogImage %}
    {% for image in entry.eventImage.all() %}
        {{ image.url() }}
    {% endfor %}
{% endblock %}