django: managing data to show on templates - django

Question

Is there a way to somehow pre-select data in the queryset before it's gone to templates? There is this 'project' models that connects to 'project_phase' and there are 'project_phase_history' records that keep track of all status changes.
I am building reports on top of this data and show all them projects on one page and want to display only project_phase_history that were submitted for the last few days OR one most recent.
I tried doing this in the view somehow like this:
projects_to_report_on = project.objects.filter(Q(current_phase__phase__id__in=[1,2,3,4]) & Q(role_sponsor__id = sponsor_id))
projects_to_report_on.current_phase.project_phase_history_set = projects_to_report_on.current_phase.project_phase_history.filter(...)
but this doesn't help, really - all data seems to jump into the template.
I ended up passing the date into the template and generating report as something like this:
{% for s in p.current_phase.project_phase_history_set.all %}
{% if s.date_submitted >= status_start_date %}
<tr>
<td>{{ s.date_submitted }}</td>
<td>{{ s.date_end_fact|default_if_none:"-" }}</td>
</tr>
{% endif %}
{% endfor %}
but it don't not have the flexibility I am looking for.
class project(models.Model):
name = models.CharField(max_length=100, null=False, unique=True)
description = models.CharField(max_length=1024,null=True,blank=True)
current_phase = models.ForeignKey('project_phase', null=True, blank=True, related_name="current_phase")
class project_phase(models.Model):
phase = models.ForeignKey('phases')
project = models.ForeignKey('project')
is_finished = models.BooleanField(default=False)
class project_phase_history(models.Model):
project_phase = models.ForeignKey('project_phase')
date_start_plan = models.DateField(null=True, blank=False)
date_start_fact = models.DateField(null=True, blank=True)

Answer 1

Here's your problem:
projects_to_report_on.current_phase.project_phase_history_set = projects_to_report_on.current_phase.project_phase_history.filter(...)
You are setting the Manager of the reverse end of the relationship to a QuerySet. That does not work. Here's an example with blog and entry models:
>>> print(Entry.objects.all())
[<Entry: Today>, <Entry: Hello>]
>>> today = datetime.date.today()
>>> print(Entry.objects.filter(pub_date__lt=today).all())
[<Entry: Hello>]
>>> blog.entry_set = Entry.objects.filter(pub_date__lt=today())
>>> print(blog.entry_set.all())
[<Entry: Today>, <Entry: Hello>]
>>> blog.entry_set = Entry.objects.none()
>>> print(blog.entry_set.all())
[<Entry: Today>, <Entry: Hello>]
Because:
>>> blog.entry_set = Entry.objects.all()
>>> type(blog.entry_set)
<class 'django.db.models.fields.related.RelatedManager'>
This means blog.entry_set is still a Manager and calling all on a Manager will simply return all records. So don't do that. Pass the QuerySet to your template and use that:
history_set = projects_to_report_on.current_phase.project_phase_history_set.filter(...)
# add it to the context as 'history_set'
{% for s in history_set.all %}
Since you need to loop over both projects and the history of that project, I'd pass a dictionary to the template:
from django.utils.datastructures import SortedDict
# ...
project_map = SortedDict()
for project in projects_to_report_on:
project_map[project] = history_query_set_goes_here
# ...
return render(request, template, {'project_map': project_map})
And then in your template:
{% for project, history_set in project_map.items %}
<h2>{{ project }}</h2>
<ol>
{% for history in history_set.all %}
<li>{{ history }}</li>
{% endfor %}
</ol>
{% endfor %}
SortedDict is documented on the Django wiki. It maintains the order of insertion so if you retrieve the projects from the database in the correct order, they will display in the same order.