的Django如何保存排除在DATABSE申請

Question

models.py

class KEBReading(models.Model): 
    #id = models.AutoField(primary_key=True,db_column='kr_id') 
    date=models.DateField() 
    time=models.TimeField() 
    truepower_reading=models.DecimalField(max_digits=6, 
    decimal_places=2,blank=False,null=False) 
    apparentpower_reading=models.DecimalField(max_digits=6, 
    decimal_places=2,blank=False,null=False) 
    truepower_consumed=models.DecimalField(max_digits=6, decimal_places=2) 
    voltage_reading=models.IntegerField(blank=False,null=False) 
    powerfactor=models.DecimalField(max_digits=3,decimal_places=2) 

forms.py

class KEBReading_form(forms.ModelForm): 
    class Meta: 
     model=KEBReading 

     exclude=("truepower_consumed","powerfactor") 
     widgets = { 

       "date" : forms.widgets.DateInput(format="%d/%m/%Y"), 
       "time" : forms.widgets.TimeInput(format="%H:%M") 
       } 

views.py

def KEBReading1(request): 
    if request.method == "POST": 


     form = KEBReading_form(request.POST) 
     if form.is_valid(): 
      prevdate=KEBReading.objects.latest("date") 

      print prevdate.date 
      print prevdate.time 
     # q1 = KEBReading.objects.get(datetime.date.today()-datetime.timedelta(0)) 

      kr_truepower_reading = form.cleaned_data["truepower_reading"] 
      kr_apparentpower_reading = form.cleaned_data["apparentpower_reading"] 
      truepower_consumed1=kr_truepower_reading-prevdate.truepower_reading 
      powerfactor1=kr_truepower_reading-           prevdate.truepower_reading/(kr_apparentpower_reading-prevdate.apparentpower_reading) 


      form.save() 
      KEBReading.objects.filter().values("date","time","truepower_reading", 
      "apparentpower_reading","truepower_consumed","voltage","powerfactor") 
      q2=KEBReading.objects.latest("date") 

      context={'KEBReading_form':form,'q2':q2} 
      return     render_to_response('keb.html',context,context_instance=RequestContext(request)) 

     else: 
      form = KEBReading_form() 

      return render_to_response('keb.html',{'KEBReading_form':form},context_instance=RequestContext(request)) 

我要保存truepower_consumed AFTR在數據庫中計算。但它給我一個錯誤truepower_consumed列不能爲空。我已經排除了形式中的truepower_consumed。但在數據庫中，我需要保存的那場

Answer 1

您需要保存形式commit=False並分配到所需的字段合適的值，並再次保存對象。

例子：在Using a subset of fields on the form

Answer 2

def KEBReading1(request): 
    if request.method == "POST": 
    .... 
    #your code till save 
    obj = form.save(commit=False) 
    #assing your values 
    obj.truepower_consumed = truepower_consumed1 
    obj.powerfactor = powerfactor1 
    obj.save() #save 

更多細節，您應該使用form.save(commit=False)代替form.save()然後計算剩餘的兩個字段。

請看看下面的代碼骨架：

## replace form.save() with following lines 
obj = form.save(commit=False) 
## Assign values to those 2 fields after calculation 
## you can add a method on your model to do this 
obj.calculate() 

## those two values were assigned after call to calculate 
## now you can save your obj 
obj.save() 


## Method to be added in your model 
def calculate(self): 
    ## Calculate truepower_consumed 
    ## Calculate powerfactor 
    self.truepower_consumed = <calculated truepower consumed> 
    self.powerfactor = <calculated power factor>