This is a generalization of my previous question about pluralize filter:
Does lift have an equivalent of Django's tags and filters?
Tags are small piece of predefined code that can be used directly in html template, for example:
{% now "jS F Y H:i" %}
renders the time right now in the given format.
Filters
Filters operate (in html template) on the context variables in the template, for example:
{{ value|capfirst }}
if called on a value "john" will result in "John". Or:
{{ value|length }}
will render the length of the string into the template.
As you can see the filters operate on the context variables that are passed to the template.
Considering tags, you could define those yourself with snippets.
As snippet is basically a callback much as a Django tag is. You don’t get any easier syntax, though, because Lift’s templates are pure XML/Html.
<Lift:Tag.now format="jS F Y H:i" />
And the logic would be defined in
class Tag {
def now: NodeSeq = // ...
}
Filtering is something you generally can’t do in a Lift template because Lift doesn’t allow any variables in a template. The whole concept is thus inapplicable. (You could do XML transforms or or bind magic but that would be a bit too much for a simple value.length.)
No, if you need the length of some value in your Html, you will have to define that inside the snippet and expose it.
If you really can’t live without filters in your template (though I can assure you, it is a good thing to separate all HTML template and code and it works once you are used to it), have a look at Scalate which may be used together with Lift as well.
This kind of logic should be in the render method of a snippet. Display code in pure Scala (rather than in a template language hybrid) is a first-class citizen with respect to testing, IDE's and refactoring tools.
These kinds of transforms don't come built-in, but you can add them with implicits:
class HappyString(s: String) {
def capfirst = ....
}
implicit def toHappyString(s: String) = new HappyString(s)
Then call these in your render method before binding whatever value it is you're generating.
Related
I'm trying to use template variable to access templates dictionaries
when I do {{ pair_name.8 }} it works
but {% with xx=8 %}{{ pair_name.xx }}{% endwith %} doestnt work, please help
I'm trying to use template variable to access templates dictionaries.
The Django template language is deliberately restricted to prevent subscripting, function calls (with parameters), etc. This is to discourage people from writing business logic in the template.
You can implement a custom template filter to perform a subscript lookup, or work with the Jinja template engine. But probably a more elegant way to do this is to alter the view, and prepare the logic in a more accessible way.
For example if you need the xx-th item, in the view, you perform a mapping with:
def some_view(request):
pair_names = [] # some data
xx = 8
data = [pair_name[xx] for pair_name in pair_names]
context = {'pair_names': data}
return render(request, 'some_template.html', context)
Processing this in the view is not only more elegant, but often more efficient as well, since the template engine often is less efficient in walking through data structures.
#Peace Bytheway - Just my 2 cents- Templates should be as dumb as possible which means try and avoid heavy logic from your template into the view. Ideally, you should also keep the view lightweight. Not much processing. The concept behind the view is to simply delegate. So, separating responsibilities into the right layer is very crucial.
I want to achieve something like this within a Django template.
{{ variable.function(parameter) }}
Where variable is a variable passed through a context to a template, in this case, an instance of a model.
I have tried different methods, but no one seems to work.
This is not possible in Django templates: they are crippled on purpose in order to prevent template designers from shooting themselves in the foot. The reasoning is that the only logic in templates should be presentation logic and all business logic should be kept in the view. Some people thinks it is fair enough and some think it is a bit condescending (those dumb template designers are not smart enough to use functions and methods safely).
I can think of 3 choices:
use jinja2 instead.
write a custom template filter.
keep all the logic in the view where Django designers think you are supposed to keep it.
I will not explain how to use Jinja2 because it is already explained in the docs and because the example in the question works verbatim if you switch to it instead of native Django templates. This simply works in Jinja2:
{{ variable.function(parameter) }}
Now the template filter solution: first you must follow a code layout convention. The filter itself would be something like this:
# at your_tag_library.py
#register.filter(name='call_with')
def apply_callable(callable, arg):
return callable(arg)
Then in the template you can do:
{% load your_tag_library %}
{{ variable.function|call_with:parameter }}
Of course the last option is the one from Daniel's answer - precompute the value in the view and just display the result in the template:
context['result'] = variable.function(parameter)
And in your template you just need {{ result }}.
There is no way to do this.
You can create another variable and pass it through the context so you could use it.
Like:
context['result'] = variable.function(parameter)
In your view.
And in your template:
{{ result }}
Imagine the context variable {{ url }} outputs www.example.com/<uuid-string> where <uuid-string> is different every time, whereas the former part of the URL stays the same.
Can one change the output of {{ url }} to instead www.forexample.com/<uuid-string>, via solely manipulating the string in the template and without involving views.py (which I know is the better way to do it, but that's not the question).
An illustrative example would be great.
read about filters and templatetags - they are a methods that allows you to perform some actions on variables in templates.
You can also create your own tags and filters that allow you to perform action non-built into Django template language
Simple example of such filter:
#in templatetags.py
#register.filter(name='duplicate')
def duplicate(value):
return value*2
#in your template
<p> {{ url|duplicate }} </p>
You can find more examples here. Also there you will find tutorial how to use and create them
If anyone here is ASP.NET pro, you might know what I mean by user control. I wish to create a similar one in django instead.
So, my problem is that I have several pages in my website, but I need a search bar to appear in every pages. Since I require the views.py to operate this search bar, I cannot do a simple method of
{% include 'something.html' %}
Therefore, can anyone suggest how can I do it?
There are a couple of ways to accomplish what you're wanting to do:
Context Processors
Template Tags
Context Processors can augment the template context with values, regardless of which template is loaded. They are akin to filters in Rails.
Template Tags, like Context Processors, can accomplish anything you can do in Python, but are implemented at the template level.
If you need something to be present on every template, one of the simplest ways to accomplish this is with an inclusion tag, which can also accept values passed to it. An inclusion tag could be implemented at your highest level template, a.k.a your MasterPage, and as long as you don't put it in a block and override it, it would appear on every page that includes that template in its inheritance chain.
If it's just something you want to include on every page, and it doesn't need to do any processing, you should just be able to place the code you want in the top-most template and have subsequent templates inherit that.
I typically have a "base.html" template that all of my templates inherit from. If I need something to be in every page, I put it there. If it's something I want there by default, but want to be able to augment it in subsequent templates, I will place it into a block. That block will let you include or override its default content.
I know this post is kind of old but I just came across it and found a kind-of-solution that works. I call it kind-of-solution because it is a workaround.
I have a few different sites on which I want to display logging information. This display always looks the same (it has the same html) and has the same database table and model class behind it.
My solution/workaround uses the django filters:
in views.py I put the list of log-entries in the context
context = {'list_log': Log.objects.filter(condition = True) }
template = loader.get_template('my_html_file.html')
return HttpResponse(template.render(context, request))
in my_html_file.html I use a custom filter
{{ list_log|get_log_uc|safe }}
in the filters.py I load another html file with this custom filter
#register.filter
def get_log_uc(list_log):
template = loader.get_template('user_control_log.html')
context = { 'list_log' : log }
return template.render(context)
in user_control_log.html I have the user control equivalent html
{% for log in list_log %}
<p>log.something</p>
{% endfor %
Is there a function that returns a list of fields that are expected in template? For example, I have the following template:
hello i am {{ name }}. {% for i in docs %} i have doc {{ i }}
Written in file. And i want to get a dict which contains:
{'name': 'str', 'docs': 'list'}
Is there something like that or i have to write it by myself?
As far as i know, NO....
Your template contains some html and some place holders (and may be something else). What render_to_template doing is, it gets a context dictionary which contain some keys and some data attached to that keys and a template. Then it places the values to those place holders according to their key names, execute some loops or condition checks if your template contains control flows like {% if...%} or {%for....%}
If TEMPLATE_DEBUG is closed in your settings, and if there is a place holder with no matching key in your context dictionary, then it will skip that without raising any error.
Also, if you pass a form object to your template and place your object directly to template as it is (without calling each field separately) [ex: {{form}} or {{form.as_p}} then django will check for fields on the form and palce them as it is shown here. In a such situation, you will only know that form is used. You have to check which fields are used from your Form definition.
If you look through that process, you must know what you need to place your context dictionary. You may write a parser to parse your template but it is far more difficult than just examining the template and find missing data, i guess.
The builtin {% debug %} tag may be helpful for you, however I don't know if I fully understand what you are asking. Basically, if you put the debug tag in your template it will print a lot of useful stuff, including all the variables available in your template.
Perhaps you could take a look at the source code for the debug tag (because they have access to all the variables there), and build a custom tag tag based off of this. Taking a glance at the source, this seems like it would be really simple to do.