Clarifying Resource Lookups in Layout: Nil Pointer

support
1

I’m having trouble understanding the object returned from resource lookup and why I can’t get a permalink in certain contexts.

Background:
Trying to use resources for image lookup in order to auto generate blog summary with title image. One method for single pages (1) works. For the list layout (2), though, I can return an image resource (it finds it), but can’t seem to evaluate Permalink or any attributes for that matter when assigned to a variable.

I am wondering if, because one of the pages does NOT have a title image, and hence returns nil, calling a lookup on a variable containing nil pops the error and I need a logic step to prevent lookups on empty sets.

Example Page: **All pages use same archetype, though ONE of them purposefully does NOT have a title_img

---
title: "Testpost"
date: 2019-06-21T23:36:58-06:00
tags: []
draft: true

resources:
-   src: "mango1.jpg"
    name: "title_img"
    params:
        ref: "101"
        alt: "Beautiful Woman"
---

TestPost Content Text Below Frontmatter

<!-- {{< figure src="mango1.jpg" title="babe for sure" >}} -->

Trying to get the picture by resource…

(1) Working resource call for single.html:

{{ define "main" }}
BLOG SINGLE HTML
<h1>{{ .Title }}</h1>
<div class="container">
    <main id="main">
        {{ range .Resources.Match "title_img" }}
        <img src="{{ .Permalink }}" alt="{{ .Params.alt }}"> 
        {{ end }}
        <p>
            {{ .Content }}
        </p>
    </main>
</div>
{{end}}

(2) List Layout - Yields execute fail: executing “main” at <$title_img.Permalink>: nil pointer evaluating resource.Resource.Permalink.

{{ define "main" }}
BLOG LIST HTML
<ul>
    {{ range .Pages }}
    <li>
        <a href="{{ .Permalink }}">{{.Date.Format "2006-01-02"}} | {{.Title}}</a>
        {{ $title_img := .Resources.GetMatch "title_img" }}
        <h4>{{ $title_img.Permalink }}</h4>
    </li>
    {{ end }}
</ul>
{{ end }}

Thanks!!

2

Answered my own question. Changed list template to:

{{ define "main" }}
BLOG LIST HTML
<ul>
    {{ range .Pages }}
    <li>
        <a href="{{ .Permalink }}">{{.Date.Format "2006-01-02"}} | {{.Title}}</a>
        {{ $title_img := .Resources.GetMatch "title_img" }}
             {{ if not $title_img }}
            <img class="card-img-top" src="https://via.placeholder.com/350x200?text=More+Than+Words" alt="Placeholder Image">
            {{ else }}
            {{ $thumbnail := $title_img.Fill "350x200" }}
            <img class="card-img-top" src="{{ $thumbnail.Permalink }}" alt="{{ $title_img.Params.alt }}">
            {{ end }}
    </li>
    {{ end }}
</ul>
{{ end }}

And voila.