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I want to do exactly this: Multi-step & bi-directional relations with relatedTo (#1640)

Common example: Let’s say you have Books, Authors, and Publishers, and two relationship fields on the Books channel: author and publisher. On a Publisher’s page, you want to list all of the Authors that have published books with them.

Here’s what I’ve tried:

{% set bookIds = craft.entries()
.section('books')
.relatedTo({ targetElement: publisher, field: 'publisher' })
.ids() %}

{% set authors = craft.entries()
.section('authors')
.relatedTo({ sourceElement: bookIds, field: 'books' })
.all() %}

However the code results in an "Undefined offset: 0" error. The error seems to occur in the first block of code.

Additionally, I'm not sure about the field in the penultimate line, shouldn't it be 'authors' rather than 'books'?

  • Search your logs (craft/storage/runtime/logs/craft.log, etc.) for the error message you’re getting. Can you post the stack trace that gets logged with it? – Brandon Kelly Oct 17 '17 at 10:42
  • Yes you’re right, field: 'books' should have been field: 'author'. Just updated the GH issue. – Brandon Kelly Oct 17 '17 at 10:46
  • Thank you Brandon, here's the log: textuploader.com/d4uuk – Rivu Meyano Oct 17 '17 at 12:30
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The error you’re getting is a bug in Craft. (Just fixed that for the next release.)

To work around it, replace the {% set authors ... %} tag with:

{% if bookIds|length %}
    {% set authors = craft.entries()
        .section('authors')
        .relatedTo({ sourceElement: bookIds, field: 'books' })
        .all() %}
{% else %}
    {% set authors = [] %}
{% endif %}
|improve this answer|||||
  • Thanks very much Brandon, but it appears to be giving the same error: textuploader.com/d4uwl – Rivu Meyano Oct 17 '17 at 15:36
  • @RivuMeyano What does {{ dump(bookIds) }} output for you? – Brandon Kelly Oct 17 '17 at 15:38
  • If I only include that in my template, then I get and "Unknown "dump" function" error, but I guess that's because bookIds hasn't been defined. It appears to be the first block of code that gives the "Undefined offset: 0" error, but if I include that in order to have the Dump function do something, I will of course still get the "Undefined offset: 0" error. – Rivu Meyano Oct 17 '17 at 16:01
  • Sorry, you should enable Dev Mode first. (Set 'devMode' => true in craft/config/general.php.) And you should put that tag after the {% set bookIds = ... %} tag, but remove the author code after it. – Brandon Kelly Oct 17 '17 at 16:02
  • Ah - here's what Dump gives me: pictr.com/image/UwhxP – Rivu Meyano Oct 17 '17 at 16:06

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