在Django模型中以某种格式创建自动ID

Question

我试图在某个实例以特定方式自动创建的模型中创建一个字段。下面是相关代码：

models.py

class Student(models.Model): 
    # This first field is what I'm focusing on 
    student_id = models.CharField(max_length=128, unique=True) 
    first_name = models.CharField(max_length=128) 
    last_name = models.CharField(max_length=128) 
    ssn = USSocialSecurityNumberField(null=False) 
    gender = models.CharField(max_length=128, choices=GENDER_CHOICES) 
    dob = models.DateField(auto_now=False, auto_now_add=False, db_column="date of birth") 
    address = models.CharField(max_length=128) 
    city = models.CharField(max_length=128) 
    state = USStateField(choices=STATE_CHOICES, default='NJ') 
    zipcode = USZipCodeField(blank=True) 
    country = CountryField(default='US', blank=True) 
    home_phone = models.CharField(max_length=128) 
    cell_phone = models.CharField(max_length=128) 
    email = models.EmailField(max_length=254, validators=[validate_email]) 
    background = models.CharField(max_length=128, choices=BACKGROUND_CHOICES) 
    # This field is relevant 
    location = models.CharField(max_length=128, choices=LOCATION_CHOICES, default='south_plainfield') 
    workforce = models.CharField(max_length=128, choices=WORKFORCE_CHOICES, default='--') 
    source = models.CharField(max_length=128, choices=SOURCE_CHOICES, default='individual') 
    refer_by = models.CharField(max_length=128, choices=REFER_BY_CHOICES, default='no refer') 
    last_status = models.CharField(max_length=128, choices=LAST_STATUS_CHOICES, default='followup') 
    newsletter = models.BooleanField() 
    created_by = models.CharField(max_length=128) 
    # This field is relevant 
    date = models.DateField(auto_now=False, auto_now_add=False) 
    notes = models.TextField() 

我想使它在一定的格式自动创建，使student_id数据领域的不同：

AASSSYYMMDD

AA为“ AV'，当学生没有付款时，'PS'。我现在默认为'PS'，所以不用担心。

SSS是大写的位置的前三个字母

YYMMDD是年，月，日场的一天的最后两个数字分别

我听说我应该使用AutoSlugField或SlugField，但我遇到的每个示例只填充一个字段的全部内容，当我想将多个字段的某些部分放在一起时将其填充。有谁知道如何正确地从不同的领域采取适当的格式？谢谢。

编辑：下面是一些其他代码：

forms.py

class StudentForm(forms.ModelForm): 
    # STEP 1 FORM 
    # student_id = forms.CharField(max_length=128, label="Student ID") 
    # first_name = forms.CharField(max_length=128, label="First Name", widget=forms.TextInput(attrs={'class': 'form-control'})) 
    # last_name = forms.CharField(max_length=128, label="Last Name") 
    ssn = USSocialSecurityNumberField(widget=forms.TextInput(attrs={'class': 'form-control'}), label="SSN", help_text="Format: xxx-xx-xxxx") 
    # gender = forms.ChoiceField(widget=forms.Select(attrs={'class': 'form-control'}), label="Gender", choices=GENDER_CHOICES) 
    dob = forms.DateField(input_formats=['%m/%d/%Y'], widget=DateInput(format='%m/%d/%Y'), label="Date of birth", help_text="Format: mm/dd/yyyy") 
    # contact_number = forms.CharField(max_length=128, label="Contact number") 
    # address = forms.CharField(max_length=128, label="Address") 
    # city = forms.CharField(max_length=128, label="City") 
    # state = forms.ChoiceField(choices=STATE_CHOICES, initial="NJ", label="State") 
    # zipcode = USZipCodeField(label="Zipcode") 
    # country = forms.ChoiceField(choices=countries, label="Country", initial="US") 
    home_phone = forms.CharField(widget=forms.TextInput(attrs={'class': 'form-control bfh-phone', 'data-format': '+1 (ddd) ddd-dddd'}), max_length=128, label="Home phone") 
    cell_phone = forms.CharField(widget=forms.TextInput(attrs={'class': 'form-control bfh-phone', 'data-format': '+1 (ddd) ddd-dddd'}), max_length=128, label="Cell phone") 
    email = forms.EmailField(widget=forms.EmailInput(attrs={'class': 'form-control'}), max_length=254, validators=[validate_email], label="Email") 
    # background = forms.ChoiceField(choices=BACKGROUND_CHOICES, label="Background") 
    # location = forms.ChoiceField(choices=LOCATION_CHOICES, initial="south_plainfield", label="Location") 
    # workforce = forms.ChoiceField(choices=WORKFORCE_CHOICES, initial="--", label="Workforce") 
    # source = forms.ChoiceField(choices=SOURCE_CHOICES, initial="individual", label="Source") 
    # refer_by = forms.ChoiceField(choices=REFER_BY_CHOICES, initial="no refer", label="Refer by") 
    # last_status = forms.ChoiceField(choices=LAST_STATUS_CHOICES, initial="followup", label="Last status") 
    newsletter = forms.BooleanField(widget=forms.CheckboxInput(), label="Newsletter", required=False) 
    # created_by = forms.CharField(max_length=128, label="Created by") 
    date = forms.DateField(widget=forms.DateInput(attrs={'class': 'form-control'}), label="Date", help_text="Format: yyyy-mm-dd") 
    notes = forms.CharField(widget=forms.Textarea(attrs={'class': 'form-control'}), required=False, label="notes", help_text="less than 1000 characters") 

    class Meta: 
     model = Student 
     fields = ('first_name', 'last_name', 'ssn', 'gender', 'dob', 'address', 'city', 'state', 'zipcode', 'country', 'home_phone', 'cell_phone', 'email', 'background', 'location', 'workforce', 'source', 'refer_by', 'last_status', 'newsletter', 'created_by', 'date', 'notes') 

views.py

def add_Student(request): 
    form = StudentForm() 
    if request.method == 'POST': 
     form = StudentForm(request.POST) 

     if form.is_valid(): 
      form.save(commit=True) 

      return render(request, 'students/add_student_success.html', {}) 
     else: 
      print(form.errors) 

    return render(request, 'students/add_student.html', {'form': form}) 

Answer 1

的主要问题是，将这个领域是你primary_key在模型或不？

如果不是，那么主键将是Django的默认id，这是一个AutoField()。所以现在您只需手动处理student_id。

我建议什么是创建一个post_save的信号处理方法，其中，你会在我的例子在这里设置student_id领域，如：

def method_for_student_id(sender, instance, created, **kwargs): 
    if created: # else it results in an infinite loop 
     # business logic here to create the student id string 
     student_id = .... 

     instance.student_id = student_id 
     instance.save() 

post_save.connect(method_for_student_id, sender=Student) 

我希望在您的情况，可以帮助 - 让我知道这是否有效！