DRF中疑难杂症

1. 在drf序列化model时，默认只显示id而不是内容，但前端是需要外键的值。

class User(BaseModel, AbstractUser):
    is_system = models.BooleanField(null=False, blank=False, default=False, verbose_name='是否为教务人员')
    gender_choice = (('male', '男'), ('female', '女'))
    ROLE = ((0, '教务人员'), (1, '老师'))
    roles = models.IntegerField(blank=True, choices=ROLE, default=0, verbose_name='角色')
    gender = models.CharField(null=False, blank=False, choices=gender_choice, default='male', max_length=6,verbose_name='性别')
    subjects = models.CharField(blank=False, null=False, max_length=12, verbose_name="任教科目")
    u_class = models.CharField(max_length=32, verbose_name="任教班级")
    class Meta:
        verbose_name = '用户'
        verbose_name_plural = verbose_name
        db_table = 'basic_user'
        ordering = ('username',)
    def __str__(self):
        return self.username
class ClassManagement(BaseModel):
    CLASS_CHOICE = ((0, '文科'), (1, '理科'))
    class_type = models.IntegerField(null=False, blank=False, choices=CLASS_CHOICE, verbose_name="班级类型")
    class_name = models.CharField(null=True, blank=True, max_length=32, unique=False, verbose_name='班级名称')
    class_number = models.IntegerField(verbose_name="班级人数")
    class_teacher = models.ForeignKey(to=User, related_name="+", on_delete=models.SET_NULL, null=True, blank=True,verbose_name="班主任")
    class_level = models.IntegerField(verbose_name="年级", default=1)
    class Meta:
        verbose_name = '班级表'
        verbose_name_plural = verbose_name
        unique_together = ['class_name']
        db_table = 'class_management'
        ordering = ('class_name',)
    def __str__(self):
        return self.class_name

方法一、在序列化的时候，就创建一个新字段class_teacher_name,指定为serializers.CharField而且字段使用 source 这个属性，具体而言格式为：

• CharField(source='<本model中的外键>.<外键指向的model的相应属性>')

  class ClassManagementSerializer(serializers.ModelSerializer):
    class_teacher_name = serializers.CharField(source='class_teacher.username')
    class Meta:
        model = ClassManagement
        fields = "__all__"

方法二、在model中增加 @property 装饰器

class ClassManagement(BaseModel):
    CLASS_CHOICE = ((0, '文科'), (1, '理科'))
    class_type = models.IntegerField(null=False, blank=False, choices=CLASS_CHOICE, verbose_name="班级类型")
    class_name = models.CharField(null=True, blank=True, max_length=32, unique=False, verbose_name='班级名称')
    class_number = models.IntegerField(verbose_name="班级人数")
    class_teacher = models.ForeignKey(to=User, related_name="+", on_delete=models.SET_NULL, null=True, blank=True,
                                      verbose_name="班主任")
    class_level = models.IntegerField(verbose_name="年级", default=1)
    class Meta:
        verbose_name = '班级表'
        verbose_name_plural = verbose_name
        unique_together = ['class_name']
        db_table = 'class_management'
        ordering = ('class_name',)
    def __str__(self):
        return self.class_name
    @property
    def class_teacher_name(self):
        return self.class_teacher.username
 # 使用 ReadOnlyField()
class ClassManagementSerializer(serializers.ModelSerializer):
    class_teacher_name = serializers.ReadOnlyField()
    class Meta:
       model = ClassManagement
       fields = "__all__"

方法三、在serializers里使用SerializerMethodField()

class ClassManagementSerializer(serializers.ModelSerializer):
    class_teacher_name = serializers.SerializerMethodField()
    class Meta:
        model = ClassManagement
        fields = "__all__"
    def get_class_teacher_name(self, obj):
        # obj.本model中的外键.外键指向的model的相应属性
        return obj.class_teacher.username

2. model中使用choices，但是序列化的时候想要显示选项的value，但是在反序列化的时候想要接收key。

class ClassManagement(BaseModel):
    CLASS_CHOICE = ((0, '文科'), (1, '理科'))
    class_type = models.IntegerField(null=False, blank=False, choices=CLASS_CHOICE, verbose_name="班级类型")
    class_name = models.CharField(null=True, blank=True, max_length=32, unique=False, verbose_name='班级名称')
    class_number = models.IntegerField(verbose_name="班级人数")
    class_teacher = models.ForeignKey(to=User, related_name="+", on_delete=models.SET_NULL, null=True, blank=True, verbose_name="班主任")
    class_level = models.IntegerField(verbose_name="年级", default=1)
    class Meta:
        verbose_name = '班级表'
        verbose_name_plural = verbose_name
        unique_together = ['class_name']
        db_table = 'class_management'
        ordering = ('class_name',)
    def __str__(self):
        return self.class_name
class ClassManagementSerializer(serializers.ModelSerializer):
    class_teacher_name = serializers.SerializerMethodField()
    class Meta:
        model = ClassManagement
        fields = "__all__"
    def get_class_teacher_name(self, obj):
        return obj.class_teacher.username
    # 重写drf的 to_representation 方法
    def to_representation(self, instance):
        data = super().to_representation(instance)
        # data.update 语法为：model中使用choices的字段 = instance.get_model中字段名_display()
        data.update(class_type=instance.get_class_type_display())
        return data

3. django ForeignKey(外键) 设置允许为空。

class Writer(models.Model):
    name=models.CharField(max_length=60,verbose_name="名字")
class Books(models.Model):
    # null 主要是用于写入数据库使用，null默认为False,也就是说django默认是所有字段都需要有值才可以正常写入数据库。
    writer=models.ForeignKey('Writer',blank = True,null=True)