ModelSerializer in Django REST framework (DRF)

In Django, a ModelSerializer is a powerful feature provided by the Django REST framework (DRF) that simplifies the process of serializing and deserializing Django model instances to and from JSON format. It automatically generates serializer classes for Django models, reducing the amount of boilerplate code required to handle serialization and deserialization.

A ModelSerializer inherits from the Serializer class provided by DRF and is specifically designed to work with Django models. It provides default implementations for most of the serialization and deserialization operations, making it easy to work with complex models.

To use ModelSerializer, you need to define a serializer class for each Django model you want to expose through your API. The serializer class is typically defined within the serializers.py file in your app.

<span># models.py </span><span>from</span> <span>django.db</span> <span>import</span> <span>models</span>
<span>class</span> <span>Author</span><span>(</span><span>models</span><span>.</span><span>Model</span><span>):</span>
    <span>name</span> <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>100</span><span>)</span>
    <span>email</span> <span>=</span> <span>models</span><span>.</span><span>EmailField</span><span>()</span>
<span>class</span> <span>Book</span><span>(</span><span>models</span><span>.</span><span>Model</span><span>):</span>
    <span>title</span> <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>200</span><span>)</span>
    <span>author</span> <span>=</span> <span>models</span><span>.</span><span>ForeignKey</span><span>(</span><span>Author</span><span>,</span> <span>on_delete</span><span>=</span><span>models</span><span>.</span><span>CASCADE</span><span>)</span>
    <span>published_date</span> <span>=</span> <span>models</span><span>.</span><span>DateField</span><span>()</span>
    <span>is_published</span> <span>=</span> <span>models</span><span>.</span><span>BooleanField</span><span>(</span><span>default</span><span>=</span><span>False</span><span>)</span>
<span># models.py </span><span>from</span> <span>django.db</span> <span>import</span> <span>models</span>

<span>class</span> <span>Author</span><span>(</span><span>models</span><span>.</span><span>Model</span><span>):</span>
    <span>name</span> <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>100</span><span>)</span>
    <span>email</span> <span>=</span> <span>models</span><span>.</span><span>EmailField</span><span>()</span>

<span>class</span> <span>Book</span><span>(</span><span>models</span><span>.</span><span>Model</span><span>):</span>
    <span>title</span> <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>200</span><span>)</span>
    <span>author</span> <span>=</span> <span>models</span><span>.</span><span>ForeignKey</span><span>(</span><span>Author</span><span>,</span> <span>on_delete</span><span>=</span><span>models</span><span>.</span><span>CASCADE</span><span>)</span>
    <span>published_date</span> <span>=</span> <span>models</span><span>.</span><span>DateField</span><span>()</span>
    <span>is_published</span> <span>=</span> <span>models</span><span>.</span><span>BooleanField</span><span>(</span><span>default</span><span>=</span><span>False</span><span>)</span>
# models.py from django.db import models

class Author(models.Model):
    name = models.CharField(max_length=100)
    email = models.EmailField()

class Book(models.Model):
    title = models.CharField(max_length=200)
    author = models.ForeignKey(Author, on_delete=models.CASCADE)
    published_date = models.DateField()
    is_published = models.BooleanField(default=False)

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Now, let’s create a ModelSerializer for the Book model:

<span># serializers.py </span><span>from</span> <span>rest_framework</span> <span>import</span> <span>serializers</span>
<span>from</span> <span>.models</span> <span>import</span> <span>Book</span>
<span>class</span> <span>BookSerializer</span><span>(</span><span>serializers</span><span>.</span><span>ModelSerializer</span><span>):</span>
    <span>class</span> <span>Meta</span><span>:</span>
        <span>model</span> <span>=</span> <span>Book</span>
        <span>fields</span> <span>=</span> <span>'__all__'</span>
<span># serializers.py </span><span>from</span> <span>rest_framework</span> <span>import</span> <span>serializers</span>
<span>from</span> <span>.models</span> <span>import</span> <span>Book</span>

<span>class</span> <span>BookSerializer</span><span>(</span><span>serializers</span><span>.</span><span>ModelSerializer</span><span>):</span>
    <span>class</span> <span>Meta</span><span>:</span>
        <span>model</span> <span>=</span> <span>Book</span>
        <span>fields</span> <span>=</span> <span>'__all__'</span>
# serializers.py from rest_framework import serializers
from .models import Book

class BookSerializer(serializers.ModelSerializer):
    class Meta:
        model = Book
        fields = '__all__'

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In the above code, we have a Book model with three fields (title, author, and published_date). The BookSerializer is a ModelSerializer that maps to the Book model and includes all fields in the serialization.

Now, let’s explore the fields and options in the Meta class of the ModelSerializer:

1. model:

   • Specifies the Django model associated with the serializer.

2. fields:

   • Use fields to include specific fields from the model in the serializer.
   • Special values for fields:
     • '__all__': Includes all fields from the model in the serializer.
     • ['field1', 'field2', ...]: Includes only the specified fields from the model in the serializer.
     • ('field1', 'field2', ...): Same as the list format, includes only the specified fields from the model.
     • []: Excludes all fields from the model. You can manually include specific fields in the serializer.

3. exclude:

   • Use exclude to specify fields that should be excluded from the serializer.

<span># Example with 'fields' and 'exclude': </span><span>class</span> <span>BookSerializer</span><span>(</span><span>serializers</span><span>.</span><span>ModelSerializer</span><span>):</span>
    <span>class</span> <span>Meta</span><span>:</span>
        <span>model</span> <span>=</span> <span>Book</span>
        <span>fields</span> <span>=</span> <span>[</span><span>'title'</span><span>,</span> <span>'published_date'</span><span>]</span>
        <span># exclude = ['is_published'] </span>
<span># Example with 'fields' and 'exclude': </span><span>class</span> <span>BookSerializer</span><span>(</span><span>serializers</span><span>.</span><span>ModelSerializer</span><span>):</span>
    <span>class</span> <span>Meta</span><span>:</span>
        <span>model</span> <span>=</span> <span>Book</span>
        <span>fields</span> <span>=</span> <span>[</span><span>'title'</span><span>,</span> <span>'published_date'</span><span>]</span>
        <span># exclude = ['is_published'] </span>
# Example with 'fields' and 'exclude': class BookSerializer(serializers.ModelSerializer):
    class Meta:
        model = Book
        fields = ['title', 'published_date']
        # exclude = ['is_published'] 

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1. read_only_fields:
   • Use read_only_fields to specify fields that should be read-only when deserializing the data. These fields won’t be included in the update or create operations.

<span># Example with 'read_only_fields': </span><span>class</span> <span>BookSerializer</span><span>(</span><span>serializers</span><span>.</span><span>ModelSerializer</span><span>):</span>
    <span>class</span> <span>Meta</span><span>:</span>
        <span>model</span> <span>=</span> <span>Book</span>
        <span>fields</span> <span>=</span> <span>'__all__'</span>
        <span>read_only_fields</span> <span>=</span> <span>[</span><span>'is_published'</span><span>]</span>
<span># Example with 'read_only_fields': </span><span>class</span> <span>BookSerializer</span><span>(</span><span>serializers</span><span>.</span><span>ModelSerializer</span><span>):</span>
    <span>class</span> <span>Meta</span><span>:</span>
        <span>model</span> <span>=</span> <span>Book</span>
        <span>fields</span> <span>=</span> <span>'__all__'</span>
        <span>read_only_fields</span> <span>=</span> <span>[</span><span>'is_published'</span><span>]</span>
# Example with 'read_only_fields': class BookSerializer(serializers.ModelSerializer):
    class Meta:
        model = Book
        fields = '__all__'
        read_only_fields = ['is_published']

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1. extra_kwargs:
   • Use extra_kwargs to provide extra options for specific fields, such as custom validation, formatting, etc.

<span># Example with 'extra_kwargs': </span><span>class</span> <span>BookSerializer</span><span>(</span><span>serializers</span><span>.</span><span>ModelSerializer</span><span>):</span>
    <span>class</span> <span>Meta</span><span>:</span>
        <span>model</span> <span>=</span> <span>Book</span>
        <span>fields</span> <span>=</span> <span>'__all__'</span>
        <span>extra_kwargs</span> <span>=</span> <span>{</span>
            <span>'title'</span><span>:</span> <span>{</span><span>'required'</span><span>:</span> <span>True</span><span>},</span>  <span># Field-level validation </span>            <span>'published_date'</span><span>:</span> <span>{</span><span>'format'</span><span>:</span> <span>'%Y-%m-%d'</span><span>}</span>  <span># Custom date format </span>        <span>}</span>
<span># Example with 'extra_kwargs': </span><span>class</span> <span>BookSerializer</span><span>(</span><span>serializers</span><span>.</span><span>ModelSerializer</span><span>):</span>
    <span>class</span> <span>Meta</span><span>:</span>
        <span>model</span> <span>=</span> <span>Book</span>
        <span>fields</span> <span>=</span> <span>'__all__'</span>
        <span>extra_kwargs</span> <span>=</span> <span>{</span>
            <span>'title'</span><span>:</span> <span>{</span><span>'required'</span><span>:</span> <span>True</span><span>},</span>  <span># Field-level validation </span>            <span>'published_date'</span><span>:</span> <span>{</span><span>'format'</span><span>:</span> <span>'%Y-%m-%d'</span><span>}</span>  <span># Custom date format </span>        <span>}</span>
# Example with 'extra_kwargs': class BookSerializer(serializers.ModelSerializer):
    class Meta:
        model = Book
        fields = '__all__'
        extra_kwargs = {
            'title': {'required': True},  # Field-level validation             'published_date': {'format': '%Y-%m-%d'}  # Custom date format         }

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With the ModelSerializer, you can efficiently serialize and deserialize complex Django models to JSON format and easily interact with your API views. It saves you from writing repetitive serialization and deserialization code, making the development of Django REST APIs faster and more convenient.

原文链接：ModelSerializer in Django REST framework (DRF)