Re: Getting started with django templatetags

On Oct 18, 2014, at 2:24 AM, Scipion <bastien.collet1@gmail.com> wrote:

Hey,

I have started to use Django (1.6) few weeks ago and I have the following problem to resolve by using templatetags. (this is my very first templatetags draft, so I may be wrong in the way of designing it, do not hesitate to highlight anything weird).

In my template, I have a list of elements (defined in the context) : items (among 6 different django models).

According to which class an item belongs, I have to display an image or a title specific to this class (these informations can't be stored in the models). 

So basically, in my template I would like to have something like : 

    {% for item in items %}
    <h1> {% show_title_tag item %} </h1>
    <img>myPath/{% show_image_name_tag %}</img>
    {% endfor %}

I can't have more than that.

   

 @register.tag
    def show_title_tag(parser,token):
    tag_name, item = token.split_contents()
    if isinstance(item,class1):
    return MyNode(item.quote)
    elif isinstance(item,class2):
    return MyNode(item.subtitle)
    elif isinstance(item,class3):
    return MyNode(item.title)
    ...
    # basically, the field to use change for each class
 
    @register.tag
    def show_image_name_tag(parser,token):
    tag_name, item = token.split_contents()
    if isinstance(item,class1):
    return MyNode("specific image name linked to class 1")
    elif isinstance(item,class2):
    return MyNode("specific image name linked to class 2")
    ...
    # the name change at each class, and is not stored in the object

 
    class MyNode:
        def __init__(self, image_or_title_string):
            self.image_or_title_string = image_or_title_string
        def render(self, context):
        return image_or_title_string.resolve(context)





Two main questions :  

 1. I am duplicated the if-elif code. Any idea how I could do it without

    duplicating it ? I could maybe only use one tag and add an extra

    parameter (in the tag and in the render) to specify which

    information I need (either the image or the title). Really not sure

    about this …

This should not count as a suggestion of “best practices”. At all.

But if you really cannot associate your related data with a model, then I might try setting up a lookup table with the classes as the lookup key. Something like

imagelookups.py

include .models

image_table = {class1: specific_image_url_for_class1,

class2: specific_image_url_for_class2,

…}

I’m not sure that the template tag is particularly useful here; why not just cough up the image URL itself rather than an entire piece of template?

So your template tag can just set a variable to be used in your templates:

@register.simple_tag

def show_title_tag(parser, token):

    tag_name, item = token…

    return image_table[item]

hth

- Tom

    

 

 2. Can I have access to the variable and not the string in the tag code

    (after doing : tag_name, item = token.split_contents()). I imagine

    that item will be a string and not my django object. How can I

    resolve this ?

Also, here are the requirements I have to enforce : 

 - keep template very simple

 - use templatetags to solve it

 - can't modify models

 - check to which class an item belongs with a function as isinstance in

   the templatetags (not in the template)

 

Please, any suggestions are welcome here, as long as they respect the requirements. Also, remind that I am a django beginner, I am just trying to do it simple and readable, not highly effective.

Thanks.

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