Using a variable with getUrl()?

Question

I'd like to be able to use a variable with the getUrl() method so I can change the filter parameter on the entry page (user controlled) instead of in the source code:

style="background-image = url('{{ getUrl(var) }}')"

I've been trying various approaches to accomplish this: nested output tags and concatenating strings eg:

{% set myFormat = entry.format %} {% set myImageUrlString = "url('{{ myImage.getUrl('" ~ myFormat ~ "') }}')" %}
...which works in part by outputting the correct string but does not get parsed (duh me!).

Can someone set me straight on the right approach to this and/or let me know whether this is even possible? TIA

July 4th, More details...

I am using a Matrix field to create a customizable grid of images. The 'format' block type is a dropdown list that contains labels/values identical to the image transforms I've created in the CP. The source code I'm using to make this work is as follows:

{% for myBlock in product.imageMatrix.all() %}
    {% set myImage = myBlock.image.one %}
    {% if myBlock.format == "square" %}{% set myTrans = 'square' %}{% endif %}
    {% if myBlock.format == "portrait" %}{% set myTrans = 'portrait' %}{% endif %}
    {% if myBlock.format == "landscape" %}{% set myTrans = 'landscape' %}{% endif %}
    {% set myImageUrl = myImage.getUrl(myTrans) %}
    <div class="cell image-pane-bg" style="background-image: url('{{ myImageUrl }}');"></div>   
{% endfor %}

This isn't very elegant but it works. Using myBlock.format as the parameter does not.

Answer 1

You're close!

When you're querying or setting a variable with a Dropdown field you need to use either .value or .label.

It looks like you could also simplify your code a bit if the value (or label) of the dropdown is the same as your transform:

{% for myBlock in product.imageMatrix.all() %}
    {% set myImage = myBlock.image.one %}
    {% set myTrans = myBlock.format.value %}
    {% set myImageUrl = myImage.getUrl(myTrans) %}
    <div class="cell image-pane-bg" style="background-image: url('{{ myImageUrl }}');"></div>   
{% endfor %}

If you wanted to get even shorter (but less readable):

{% for myBlock in product.imageMatrix.all() %}
    <div class="cell image-pane-bg" style="background-image: url('{{ myBlock.image.one.getUrl(myBlock.format.value) }}');"></div>   
{% endfor %}