Question

I am trying to understand the following code better. It’s working, but I just don’t fully understand several elements (questions below):

from django.shortcuts import render_to_response
from mywiki.wiki.models import Page
from django.http import HttpResponseRedirect
from django import forms
import markdown

class SearchForm(forms.Form):
    text = forms.CharField(label='Enter search term')

def search_page(request):
    if request.method =='POST':
        f = SearchForm(request.POST)
        if not f.is_valid():
            return render_to_response('search.html', {'form':f})
        else:
            pages = Page.objects.filter(name__contains = f.cleaned_data['text'])
            return render_to_response('search.html', {'form':f, 'pages':pages})
    f = SearchForm()
    return render_to_response('search.html', {'form':f})

specialPages = {'SearchPage':search_page}

def view_page(request, page_name):
    if page_name in specialPages:
        return specialPages[page_name](request)
    try:
        page = Page.objects.get(pk=page_name)
    except Page.DoesNotExist:
        return render_to_response('create.html', {'page_name':page_name})

    content = page.content    
    return render_to_response('view.html', {'page_name':page_name, 'content':markdown.markdown(content)})

1. Why do we need to specify that the request.method has to be POST – wouldn’t clicking an HTML button implicitly signal an intent to change/affect something? Or POST is only appropriate when the action affects the database?

2. How does the line pages = Page.objects.filter(name__contains = f.cleaned_data['text']) work? It takes the model Page(models.Model), but what do the ‘objects’ and ‘filter’ methods do in this case?

3. In the view_page, why do we need to add (request) in return specialPages[page_name](request)

Thanks!

Answer 1

1. The POST test is used as a differentiator.

   When the view is called with GET, the form is rendered. The form specifies that it needs to be submitted with using POST, so the code assumes that a POST request signals the form is submitted.

2. The objects attribute triggers the actual database query. By adding the .filter() call you specify a more specific database query, one where the name attribute contains the value of f.cleaned_data['text']. The result is a set of database results that match that query.

3. the specialPages dictionary values are themselves views, and for these to work, you call them with the request parameter. Just like the view_page view callable itself.