檢查數據庫是否與Null字段重複

Question

我想在添加條目之前檢查數據庫中是否有重複條目。這裏是我目前的型號 -

class Education(models.Model): 
    school = models.CharField(max_length=100) 
    class_year = models.IntegerField(max_length=4, blank=True, null=True, choices=YEAR) 
    degree = models.CharField(max_length=100, blank=True, null=True) 

class UserProfile(models.Model): 
    user = models.ForeignKey(User, unique=True) 
    employments = models.ManyToManyField(Employment) 

在窗體上，用戶必須進入學校。年級和學位是可選的。要檢查重複條目，現在我有 -

if form.is_valid() and request.POST['school']: 
    school = form.cleaned_data['school'] 
    try: 
     school_object = Education.objects.get(school=form.cleaned_data['school'], 
               class_year=form.cleaned_data['class_year'], 
               degree = form.cleaned_data['degree']) 
    except (Education.DoesNotExist): 
     school_object = Education(school=form.cleaned_data['school'], 
            class_year=form.cleaned_data['class_year'], 
            degree = form.cleaned_data['degree']) 
     school_object.save() 
     profile.educations.add(school_object) 
     profile.save() 

如果沒有填寫class_date，我得到一個ValueError。如何解決這個問題，以及在檢查重複的時候？謝謝。

Answer 1

首先，除非你有一個很好的理由，否則你不應該在不通過表單發送郵件變量的情況下訪問郵政變量。

from django import forms 
class MyForm(forms.form): 
    school = forms.CharField() 
    degree = forms.CharField(required=False) 
    class_year = forms.CharField(required=False) 

    def clean(self): 
    if not self.cleaned_data.has_key('degree'): 
     self.cleaned_data['degree'] = None 
    if not self.cleaned_data.has_key('class_year'): 
     self.cleaned_data['class_year'] = None 
    return self.cleaned_data 

然後，當你正在處理的觀點：

... 
if request.method == "POST": 
    form = MyForm(request.POST) 
    if form.is_valid(): 
    try: 
     # NOTE that the objects.get method will raise MultipleObjectsReturned if the 
     # database has more than one object that matches the query 
     my_object = Education.objects.get(school=form.cleaned_data['school'], 
     class_year=form.cleaned_data['class_year'], 
     degree = form.cleaned_data['degree']) 
    except Education.DoesNotExist: 
     my_object = Education(school=form.cleaned_data['school'], 
     class_year=form.cleaned_data['class_year'], 
     degree = form.cleaned_data['degree']) 
else: 
    form = MyForm() 
... 

Answer 2

在訪問量：

if 'Add School' in request.POST.values(): 
    form = EducationForm(request.POST) 
    if form.is_valid() and request.POST['school']: 
     school = form.cleaned_data['school'] 
     try: 
      school_object = Education.objects.get(school=form.cleaned_data['school'], 
               class_year=form.cleaned_data['class_year'], 
               degree = form.cleaned_data['degree']) 
     except (Education.DoesNotExist, ValueError): 
      school_object = Education(school=form.cleaned_data['school'], 
               class_year=form.cleaned_data['class_year'], 
               degree = form.cleaned_data['degree']) 
      school_object.save() 
      profile.educations.add(school_object) 
      profile.save() 
      return redirect('edit_education') 

或者，使用get_or_create簡化：

if 'Add School' in request.POST.values(): 
    form = EducationForm(request.POST) 
    if form.is_valid() and request.POST['school']: 
     school = form.cleaned_data['school'] 
     school_object, created = Education.objects.get_or_create(school=form.cleaned_data['school'], 
              class_year=form.cleaned_data['class_year'], 
              degree = form.cleaned_data['degree']) 
     if created: 
      profile.educations.add(school_object) 
      profile.save() 
      return redirect('edit_education') 

在形式：

YEAR = ([(x, x) for x in range(1970,2015)]) 
YEAR.append((0,'Select Year')) 
YEAR.reverse() 

class EducationForm(forms.Form): 
    school = forms.CharField() 
    class_year = forms.ChoiceField(choices=YEAR, required=False) 
    degree = forms.CharField(required=False) 
    def clean(self): 
     if not self.cleaned_data.get('class_year'): 
      self.cleaned_data['class_year'] = None 
     if not self.cleaned_data.get('degree'): 
      self.cleaned_data['degree'] = '' 
     return self.cleaned_data