Django出现local variable 'Facility' referenced before assignment报错求助

报错根因 #

你导入的Facility是模型类名，但是在POST请求处理逻辑中，你把从表单获取的字段值也命名为了Facility，Python解释器会将Facility识别为当前视图函数的局部变量，执行到第一行facilities=Facility.objects.order_by('id')时，检测到后续代码对局部变量Facility有赋值操作，就会抛出“局部变量在赋值前被引用”的错误。

修复方案 #

修改POST逻辑中的局部变量名，避免和模型类名重名即可，比如改成小写开头的facility或者selected_facility，修改后的视图代码参考：

def addshift(request):
        facilities=Facility.objects.order_by('id')
        user=request.user   
        if request.method=="POST":
            StartTime=request.POST.get('StartTime')
            StartDate=request.POST.get('StartDate')
            EndTime=request.POST.get('EndTime')
            EndDate=request.POST.get('EndDate')
            # 修改变量名，避免和Facility类名冲突
            selected_facility = request.POST.get('Facility')
            Note=request.POST.get('Note')
            shift=Shift(user=request.user,StartTime=StartTime,StartDate=StartDate,EndTime=EndTime,EndDate=EndDate,Facility=selected_facility,Note=Note)
            shift.save()
            messages.success(request,"Shift added successfully!")
    
        context={
            'schedule':'active',
            'facilities':facilities,
            'user':user,
    
        }
        return render(request,'addshift.html',context)

额外注意事项 #

如果你的Shift模型中Facility是关联Facility表的外键字段，直接传递表单获取的字符串ID会报错，需要改成传递Facility实例，或者给外键字段名加_id后缀传值，示例：

# 方法1：传实例
facility_obj = Facility.objects.get(id=selected_facility)
shift=Shift(user=request.user,StartTime=StartTime,StartDate=StartDate,EndTime=EndTime,EndDate=EndDate,Facility=facility_obj,Note=Note)

# 方法2：传id给外键_id字段
shift=Shift(user=request.user,StartTime=StartTime,StartDate=StartDate,EndTime=EndTime,EndDate=EndDate,Facility_id=selected_facility,Note=Note)

内容的提问来源于stack exchange，提问作者MohZaf66