如何在Django REST API中读取外键关联模型的指定字段

假设你的模型定义如下（可与实际代码对照调整）：

# models.py
from django.db import models

class ModelA(models.Model):
    fldA1 = models.CharField(max_length=100)
    fldA2 = models.CharField(max_length=100)
    fldA3 = models.CharField(max_length=100)

class ModelB(models.Model):
    fldB1 = models.CharField(max_length=100)
    fldB2 = models.CharField(max_length=100)
    model_a = models.ForeignKey(ModelA, on_delete=models.CASCADE, related_name='model_bs')

下面提供两种常用实现方案：

方案一：嵌套序列化器 #

适合需要复用ModelA序列化逻辑，或后续可能扩展返回更多ModelA字段的场景：

# serializers.py
from rest_framework import serializers
from .models import ModelA, ModelB

class ModelASerializer(serializers.ModelSerializer):
    class Meta:
        model = ModelA
        fields = ('fldA3',)  # 仅指定需要的fldA3字段

class ModelBSerializer(serializers.ModelSerializer):
    model_a = ModelASerializer()  # 嵌套关联模型的序列化器

    class Meta:
        model = ModelB
        fields = ('fldB1', 'fldB2', 'model_a')

方案二：SerializerMethodField #

适合仅需获取关联模型单个字段、逻辑简单的场景：

# serializers.py
from rest_framework import serializers
from .models import ModelB

class ModelBSerializer(serializers.ModelSerializer):
    fldA3 = serializers.SerializerMethodField()

    def get_fldA3(self, obj):
        # 通过ModelB实例的外键关联获取ModelA的fldA3
        return obj.model_a.fldA3

    class Meta:
        model = ModelB
        fields = ('fldB1', 'fldB2', 'fldA3')

编写视图 #

使用Django REST Framework的通用视图快速实现列表/详情接口：

# views.py
from rest_framework import generics
from .models import ModelB
from .serializers import ModelBSerializer

class ModelBListAPIView(generics.ListAPIView):
    # 预加载关联ModelA，避免N+1查询问题
    queryset = ModelB.objects.select_related('model_a').all()
    serializer_class = ModelBSerializer

class ModelBDetailAPIView(generics.RetrieveAPIView):
    queryset = ModelB.objects.select_related('model_a').all()
    serializer_class = ModelBSerializer

配置路由 #

在项目urls.py中添加接口路由：

# urls.py
from django.urls import path
from .views import ModelBListAPIView, ModelBDetailAPIView

urlpatterns = [
    path('modelb/', ModelBListAPIView.as_view(), name='modelb-list'),
    path('modelb/<int:pk>/', ModelBDetailAPIView.as_view(), name='modelb-detail'),
]

内容的提问来源于stack exchange，提问作者user3282758