Django一对多关系查询

Question

Well, I'm starting learning Django and now I have problems to get a QuerySet that allows me fill a table.

The table shows information about the projects of a programer. Each project has n iterations.

|id|Name|Start|End|Cost|Objetive|Description|Client|Progress|Status| Iterations|

In the View, I can get the first 9 columns (From the Project model) using a QuerySet like this:

projects = Project.objects.filter(responsible = request.user.id)

In the 10th column I have to show the number of "Iterations" of every Project and I'm trying this:

Proyect.objects.filter(responsible = request.user.id).annotate(Niterations= Iteration.objectsfilter(project_id= request.user.id).count())

And well,it doesn't work, I understand that with an annotation the arguments will be added to each object in the QuerySet ...

The other way Iwas trying is:

projects = Project.objects.filter(responsible = request.user.id)
for proy in projects:
   proy.annotate(Iteration.objects.filter(project_id=proy.pk).count())

I don't know exactly whay it doesn't works... Is there an easier way?

It's been a little confusing ...

I'm working with two models: "Project" and "Iteration"

Model: Project

from django.db import models
from usuarios.models import User

class Proyect(models.Model):
    name = models.CharField(max_length=255)
    start = models.DateField()
    end = models.DateField(blank=True, null=True)
    cost = models.FloatField(blank=True, null=True)
    objetive = models.TextField(blank=True, null=True)
    description = models.CharField(max_length=255, blank=True, null=True)
    client = models.CharField(max_length=255, blank=True,null=True)
    progress = models.FloatField(verbose_name=u'percentage of progress', default=0.00, editable=False)
    responsible = models.ForeignKey(User, editable=False)
    STATUS_CHOICES = (
        ('A','Atrasado'),
        ('N','Normal'),
        ('AP','Alta prioridad'),        
        )
    status = models.CharField(max_length=2, choices=STATUS_CHOICES)

   def __unicode__(self):
        return self.name

Model: Iteration

from django.db import models
from proyectos.models import Project

class Iteration(models.Model):
    identifier = models.CharField(max_length=255)
    start = models.DateField()
    end = models.DateField()
    progress = models.FloatField(default=0.0, editable=False)
    project = models.ForeignKey(Project)

Thanks in advance!!!

(I translated this, sorry if there are mistakes in translations)

Answer 1

The right way is:

Project.objects.filter(responsible=request.user.id).annotate(niterations=Count('iteration')

You can see the query to understand better:

result = Project.objects.filter(responsible=request.user.id).annotate(niterations=Count('iteration')
print str(result.query)

I hope I've helped.