Side-by-side comparison of template tags in Django and Ruby on Rails

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Side-by-side comparison of template tags in Django and Ruby on Rails

Format the current time

Django

from django import template
import datetime

register = template.Library()

@register.tag
def do_current_time(parser, token):

    class CurrentTimeNode(template.Node):
        def __init__(self, format_string):
            self.format_string = format_string
        def render(self, context):
            return datetime.datetime.now().strftime(self.format_string)

    try:
        tag_name, format_string = token.split_contents()
    except ValueError:
        raise template.TemplateSyntaxError("%r tag requires a single argument" % token.contents.split()[0])
    if not (format_string[0] == format_string[-1] and format_string[0] in ('"', "'")):
        raise template.TemplateSyntaxError("%r tag's argument should be in quotes" % tag_name)
    return CurrentTimeNode(format_string[1:-1])

Ruby on Rails

def current_time format
    Time.now.strftime format

Inject a variable into the template's context

Django

from django import template

from news.models import Article

register = template.Library()

@register.tag
def get_categories(parser_token):

    class Node(template.Node):

        def __init__(self, variable_name):
            self.variable_name = variable_name
    
        def render(self, context):
            context[self.variable_name] = Category.objects.all()
            return ''

    bits = token.contents.split()

    if len(bits) != 3:
        raise template.TemplateSyntaxError, "get_categories takes exactly three arguments"
    if bits[1] != 'as':
        raise template.TemplateSyntaxError, "get_categories' second argument must be 'as'"

    return Node(bits[2])

Ruby on Rails

def categories
    Category.all

Why so much Python code to get your categories ?
Tried Django context processors ?

def categories(request):
    return {'categories': Category.objects.all()}

BTW thanks for django-kronos... it helps me a lot (or it will help my app users, not familiar with crontabs...)

Why so much Python code to get your categories? Tried Django context processors?

Well, context preprocessors are applied to every single template in your application.

BTW thanks for django-kronos... it helps me a lot (or it will help my app users, not familiar with crontabs...)

You're welcome!

You're right for context_preprocessors... processed ever if you don't need them...

There is also the 'simple_tag' syntax :

def do_current_time(format_string):
    return datetime.datetime.now().strftime(format_string)
register.simple_tag(do_current_time)

Still longer than ruby, I have to admit... :-)

You could pass the current time to the context and then use the built-in filter https://docs.djangoproject.com/en/dev/ref/templates/builtins/#time, i.e. {{ value|time:"H:i" }}

Or the built-in template tag "now": https://docs.djangoproject.com/en/dev/ref/templates/builtins/#now, i.e. It is {% now "jS F Y H:i" %}