OnetoOneField Django query

Question

so I have this two models:

class Patient(models.Model):
    patientID = models.CharField(max_length=200 , default='Enter PatientID')
    age = models.IntegerField(default='-')
    gender = models.CharField(max_length=200,choices=Gender_Choice, default='UNDEFINED')

class RiskFactor(models.Model):
    patient = models.OneToOneField(Patient, on_delete=models.CASCADE)
    hypertension = models.BooleanField(default=False)
    diabetes = models.BooleanField(default=False)
    PAVK = models.BooleanField(default=False)
    nicotin = models.BooleanField(default=False)

So I've changed from ForeignKey to OnetoOneField because of reasons. So with the ForeignKey everything was easypeasy and I can show the data of the RiskFactor model in my Patient detail template. Now I have problems to change the query. I just don't know how to change this:

<ul>
  {% for rfac in patient.riskfactor_set.all %}
   <li>Hypertension: {{ rfac.hypertension }}<br/>
      Diabetes: {{ rfac.diabetes }}<br/>
      PAVK: {{ rfac.PAVK }}<br/>
      Nicotin: {{ rfac.nicotin }}<br/>
   </li>
   {% endfor %}
</ul>

into sth that shows the riskfactor data from the patient with a OneToOneRel.

Thanks for your help!

Answer 1

I would add related_name="risk_factor" to your OneToOneField declaration, just to make it more clear how to reference the associated RiskFactor. From there, you can reference it like any other property of patient - it no longer is a list, but a single object. Like so below

<ul>
  {% with patient.risk_factor as rfac %}
    <li>Hypertension: {{ rfac.hypertension }}<br/>
      Diabetes: {{ rfac.diabetes }}<br/>
      PAVK: {{ rfac.PAVK }}<br/>
      Nicotin: {{ rfac.nicotin }}<br/>
    </li>
  {% endwidth %}
</ul>

You can do without the with statement, but it makes it easiest to convert your code, plus then you would have to put patient.risk_factor. before every property you want, so might as well save it to rfac.

Answer 2

Your trying to query a set of a one to one relationship which isn't possible. Since every Patient can only have 1 RiskFactor.

Why don't you get the risk factors based on the patient and pass it into the template like this:

patient_risk = RiskFactor.objects.get(patient=patient)

ctx = {
    'rfac': patient_risk
}

Then in your template you could access the risks for that particular patients.

<ul>
   <li>Hypertension: {{ rfac.hypertension }}<br/>
      Diabetes: {{ rfac.diabetes }}<br/>
      PAVK: {{ rfac.PAVK }}<br/>
      Nicotin: {{ rfac.nicotin }}<br/>
   </li>
</ul>

You can also query all of the RiskFactors models and access the patient via RiskFactor.patient if you want to loop over all patients who have RiskFactors.

all_risk_factors = RiskFactor.objects.all()

ctx = {
    'risk_factors': all_risk_factors
}

<ul>
  {% for risk in risk_factors %}
   <li><strong>Patient ID: risk.patient.patientID</strong></li>
   <li>Hypertension: {{ risk.hypertension }}<br/>
      Diabetes: {{ risk.diabetes }}<br/>
      PAVK: {{ risk.PAVK }}<br/>
      Nicotin: {{ risk.nicotin }}<br/>
   </li>
   {% endfor %}
</ul>