Children like support for macros / included templates

[michalvankodev]

So I did some research and I'd like to open this as a discussion because I haven't been able to find a good solution to this convention.

Problem

Just like in many other templating languages, I'd like to create a wrapper component template that can be re-used with different content inside the template.

This is in some frameworks referred to as <slot/> or children in react.

With Jinja this pattern is possible with the caller functionality with macros: https://jinja.palletsprojects.com/en/3.0.x/templates/#call

Workaround Example

My current solution is to create 2 macros and put the content in between.
This can however cause a few problems when used incorrectly.

  {% call sc::social_card_start("profile", "Beautiful header content goes here") %}
    <span> Here I have total freedom unrelated to the rest of the <code>social_card</code> component </span>
  {% call sc::social_card_end() %}

{% macro social_card_start(svg, heading) %}

<section class="border rounded-md bg-pink-200 m-4 p-4">
	<header class="flex text-center justify-center items-center gap-2 mb-2">
		 <svg aria-hidden="true" class="h-7 w-7 fill-blue-950">
	    <use xlink:href="/svg/icons-sprite.svg#{{svg}}" />
	  </svg>
		<h3 class="text-lg font-medium mb-1">{{heading|safe}}</h3>
	</header>

{% endmacro %}

{% macro social_card_end() %}
	</section>
</section>
{% endmacro %}

Resolution

I've seen that the support for caller was multiple times declined: #996 #930

This brings me to a question: How should I approach creating and using templates that are meant to wrap around different content?

[djc]

I think the standard approach would be to use template inheritance? (To be clear, you can have multiple levels of inheritance IIRC.)

(Sorry for the slow response.)

[michalvankodev]

I think the standard approach would be to use template inheritance? (To be clear, you can have multiple levels of inheritance IIRC.)

I have no idea how can this be done with template inheritance.

I am not able to use {% extends %} in a child template. But extending doesn't make sense anyway. I want to display multiple components with the same template.

Maybe it is not clicking to me how can I use this but I'd need to define all component templates in the base.html template so they can be used. Each component must have prefixed block names so they don't overwrite each other when used. Another thing is either I write another template for each usage of the component or I just write a big {% let .... %} bindings prior to importing each time.

This all applies if I understand correctly how this works. Either way, this doesn't help make the code modular. More the other way around.

[djc]

I guess I don't understand your use case very well. Are you aware, too, that templates implement Display as well, so you can easily nest templates (that is, just pass a value that itself implements Display and render it). Maybe consider a minimal full example of what you're trying to do and why macros/inheritance/includes/nested templates are not sufficient.

[michalvankodev]

I am aware of that. From my workaround example it should be easy to understand that I am just creating a reusable wrapper component. I want to allow parent template to be the one that sends the content into the child template. I want to do this within the templates themselves.

Another example could be this:

{% macro social_card(svg, heading, content) %}

<section class="border rounded-md bg-pink-200 m-4 p-4">
	<header class="flex text-center justify-center items-center gap-2 mb-2">
		 <svg aria-hidden="true" class="h-7 w-7 fill-blue-950">
	    <use xlink:href="/svg/icons-sprite.svg#{{svg}}" />
	  </svg>
		<h3 class="text-lg font-medium mb-1">{{heading|safe}}</h3>
	</header>
        {{content}}
</section>
{% endmacro %}

{% call sc::social_card(
"profile", 
"Beautiful header content goes here",
"<span> Here I have total freedom unrelated to the rest of the <code>social_card</code> component </span>"
)

[djc]

I think this is something I would use nested template types for, that seems to map well to "reusable wrapper component"?

[JElgar]

I think I'm struggling with a similar issue and Im not sure how to solve it.

I want to create a "Card" component (Similar to https://ui.shadcn.com/docs/components/card), so in the simplest case just a div with some styling that has a child component (and in more complex cases maybe it has multiple blocks).

An example page I want to create is 2 cards next to each other with different children (e.g. one with a table in it and one with some text)

Ive tried a few things:

I tried to use a macro, that works great until I need the child to be more than just text (some html elements). Im not sure if/how I can pass html as an argument to a macro.

I tried to use inheritance. I created a card component with a content block. I could then create components which extended that card (e.g. a text card and a table card) but it wasn't clear how to avoid creating lots of files in this case. e.g. If I have:

// card.html
<div
  class="p-6 bg-white rounded-lg shadow-md dark:bg-slate-600 dark:border-gray-700 dark:text-white"
>
  {% block content %}{% endblock %}
</div>

I can easily extend this to create a fancy stat card for example:

// stat_card.html
{% extends "card.html" %}

{% block content %}

<div class="w-full">
    <div class="mt-3 sm:mt-0 sm:ml-1">{% block value %}{% endblock %}</div>
  <h1>{% block title %}{% endblock %}</h1>
</div>

{% endblock %}

But then if I want 3 of these card in index.html how would I add them?

I could create 3 files, one for each card and then include each of those files. Im not a huge fan of that because I need lots of files (each file only exists to define 2 string values to input into the template)

But it would be nice if I could have a syntax like the macro and do

    {% call cards::stat_card("foo", 3) %}
    {% call cards::stat_card("bar", 2) %}

but it doesn't seem possible to create a macro which contains an extends within it?

[couchand]

If I'm understanding your use-case correctly, you can solve this in Rust rather than in the template itself.

#[derive(Template)]
#[template(text = "<div>{% for child in children %}{{ child }} {% endfor %}</div>, ext = "html")]
struct Container<Child: Template> {
    children: Vec<Child>,
}

Though you mention that you want to do this within the templates themselves. Is there a reason that building the structure in Rust is not an option here?