DRF learning notes (II): Data deserialization

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Preface

This blog is written after the last blog , Sure Click here see

One 、 Data deserialization use

1、 Basic use

When deserializing with a serializer , You need to verify the data , To obtain the data that has been successfully verified or save it as a model class object .
Before getting the deserialized data , Must call is_valid() Method validation , Verification successful return True, Otherwise return to False.
Use ：

>>> from demo.serializer import ClassInfoSerializer
>>> data = {
    'number': ' One ', 'grade': ' Third grade '}
>>> serializer = ClassInfoSerializer(data=data)
>>> serializer.is_valid()
False
>>> serializer.errors
{
    'number': [ErrorDetail(string='A valid integer is required.', code='invalid')]}

2、 Custom validation

If you feel that the provided verification method is not enough , You can also customize the validation , There are three ways ：

（1）validators

Add... To the field validators Option parameters , You can also supplement the verification behavior , Modify the code ：

#  Validation function 
def about_grade(value):
    if not (value == ' In grade one ' or value == ' second grade ' or value == ' Third grade '):
        raise serializers.ValidationError(" Grade input error ！")

class ClassInfoSerializer(serializers.Serializer):
    """ Class data serializer """
    id = serializers.IntegerField(label='ID', read_only=True)
    number = serializers.IntegerField(label=' Class number ', required=False)
    grade = serializers.CharField(label=' grade ', max_length=3, required=False, validators=[about_grade])
    studentinfo_set = serializers.PrimaryKeyRelatedField(read_only=True, many=True)  #  add to 

Use ：

>>> from demo.serializers import ClassInfoSerializer
>>> data = {
    'grade': ' Fourth grade '}
>>> serializer = ClassInfoSerializer(data=data)

result

（2）validate_<field_name>

Right <field_name> Field , You can also modify the code as follows ：

class ClassInfoSerializer(serializers.Serializer):
    """ Class data serializer """
    id = serializers.IntegerField(label='ID', read_only=True)
    number = serializers.IntegerField(label=' Class number ', required=False)
    grade = serializers.CharField(label=' grade ', max_length=3, required=False)
    studentinfo_set = serializers.PrimaryKeyRelatedField(read_only=True, many=True)  #  add to 
    def validate_grade(self, value):
        if not (value == ' In grade one ' or value == ' second grade ' or value == ' Third grade '):
            raise serializers.ValidationError(" Grade input error ！")

Use ：

>>> from demo.serializers import ClassInfoSerializer
>>> data = {
    'grade': ' Fourth grade '}
>>> serializer = ClassInfoSerializer(data=data)

result ：

（3）validate

If you need to compare and verify multiple fields at the same time , Can define validate Method to verify , The code is modified as follows ：

class ClassInfoSerializer(serializers.Serializer):
    """ Class data serializer """
    id = serializers.IntegerField(label='ID', read_only=True)
    number = serializers.IntegerField(label=' Class number ', required=False)
    grade = serializers.CharField(label=' grade ', max_length=3, required=False)
    studentinfo_set = serializers.PrimaryKeyRelatedField(read_only=True, many=True)  #  add to 
    def validate(self, attrs):
        number =attrs['number']
        grade = attrs['grade']
        if number > 10:
            raise serializers.ValidationError("number Not greater than 10")
        if not (grade == ' In grade one ' or grade == ' second grade ' or grade == ' Third grade '):
            raise serializers.ValidationError(" Grade input error ！")

Use ：

(InteractiveConsole)
>>> from demo.serializers import ClassInfoSerializer
>>> data = {
    'number': 11, 'grade': ' Fourth grade '}
>>> serializer = ClassInfoSerializer(data=data)
>>> serializer.is_valid()
False
>>> serializer.errors
{
    'non_field_errors': [ErrorDetail(string='number Not greater than 10', code='invalid')]}
>>> data = {
    'number': 5, 'grade': ' Fourth grade '}
>>> serializer = ClassInfoSerializer(data=data)
>>> serializer.is_valid()
False
>>> serializer.errors
{
    'non_field_errors': [ErrorDetail(string=' Grade input error ！', code='invalid')]}

Two 、 preservation

If after successful verification , Want to be based on validated_data Finish creating data object , By implementing create() and update() Two ways to achieve （ Add ). Add the following code ：

    def create(self, validated_data):
        """ newly build """
        return ClassInfo.objects.create(**validated_data)
    def update(self, instance, validated_data):
        """ to update ,instance For the object instance to be updated """
        instance.number = validated_data.get('number', instance.number)
        instance.grade = validated_data.get('grade', instance.grade)
        instance.save()
        return instance

After implementing the above two methods , When deserializing data , You can go through save() Method returns a data object instance .
If you create a serializer object , Pass on data Data time , Call save() Method time ,create() Called , contrary , If it's delivered instance example , Call save() Method time ,update() Called .

Use ：
add to ：

>>> from demo.serializers import ClassInfoSerializer
>>> data = {
    'number': 2, 'grade': ' Third grade '}
>>> serializer = ClassInfoSerializer(data=data)
>>> serializer.is_valid()
True
>>> serializer.save()
<ClassInfo: ClassInfo object (4)>

result ：
stay navicat Data has indeed been added to view

to update ：

>>> from demo.models import ClassInfo
>>> Class_data = ClassInfo.objects.get(id=2)
>>> data = {
    'number': 3, 'grade': ' Third grade '}
>>> serializer = ClassInfoSerializer(Class_data, data=data)
>>> serializer.is_valid()
True
>>> serializer.save()
<ClassInfo: ClassInfo object (2)>

result ：
stay navicat The data has indeed been updated

Next chapter ：DRF Learning notes ( 3、 ... and )： Model class serializer ModelSerializer