If-else and for loops not working in HTML for new XBlock in OpenEdX

Question

I've created a new XBLock and trying to pass data from python file to HTML file, but the standard template syntax is throwing error, HTML file code below

<p>EdlyCarouselXBlock: count is now
    <span class='count'>{self.count}</span> (click me to increment).
    {{ self.count }}
    {% if self.count%}
    <p>Simple If</p>
    {%endif%}
</p>
<p id="decrement">(click me to Decrement).</p>
</div>

It is supporting a single bracket to access values {self.name}, for loops & if-else it throws an error. Tried using python 3.6.5 & 3.8.0, the same issue on both versions, any help would be appreciated, same issue in the lms/cms as well.

Answer 1

Solve the issue, posting the solution for future references. Default xblock is created without using Django templating so we need to configure it manually.

Following default student_view function is added

def student_view(self, context=None):
    """
    The primary view of the SampleXBlock, shown to students
    when viewing courses.
    """
    html = self.resource_string("static/html/sample.html")
    frag = Fragment(html.format(self=self))
    frag.add_css(self.resource_string("static/css/sample.css"))
    frag.add_javascript(self.resource_string("static/js/src/sample.js"))
    frag.initialize_js('SampleXBlock')
    return frag

so in order to involve Django template rendering make the following changes. include template and context

from django.template import Context, Template

# Add this method in your xblock class

def render_template(self, template_path, context={}):
    template_str = self.resource_string(template_path)
    template = Template(template_str)
    return template.render(Context(context))

def student_view(self, context=None):
    """
    The primary view of the SampleXBlock, shown to students
    when viewing courses.
    """
    frag = Fragment()

    html = self.render_template("static/html/sample.html", {'count': self.count})
    frag.add_content(html)
    frag.add_css(self.resource_string("static/css/sample.css"))
    frag.add_javascript(self.resource_string("static/js/src/sample.js"))
    frag.initialize_js('SampleXBlock')
    return frag