django后臺中有一個(gè)模型的所有字段無法顯示，也無法在后臺中手動(dòng)添加該模型新記錄。用shell查看數(shù)據(jù)庫，發(fā)現(xiàn)數(shù)據(jù)存在，應(yīng)用也運(yùn)行正常。其余模型均能正常顯示，不知道什么原因。django版本是1.11

models.py

from django.db import models

class User(models.Model):
        openid = models.CharField(max_length=20)
        nickname = models.CharField(max_length=20,null=True)
        def __str__(self):
                return self.nickname

class Record(models.Model):
        expression = models.CharField(max_length=100)
        user = models.ForeignKey(User)
        time = models.DateTimeField(auto_now_add=True)
        def __str__(self):
                return self.expression

admin.py

from django.contrib import admin
from .models import User,Record

class RecordAdmin(admin.ModelAdmin):
        list_display = ('expression','user','time')

class UserAdmin(admin.ModelAdmin):
        empty_value_display = "空"
        list_display = ('openid','nickname')

admin.site.register(User,UserAdmin)
admin.site.register(Record,RecordAdmin)