Understanding of serializer

In fact, it is the naming style of Django restful frameworkrestful API, mainly because front-end and back-end separation occurs in front-end and back-end separation development: the user accesses the server of static files, and all the data is sent to the restful style by Ajax requests: data should be a term, and the verb is returned to the front-end by an HTTP request method to express the restful style API. No matter what Request Method

"'Features: repeated
Because no matter what request method, the object content must be returned to the front-end, which is in JSON format.
Therefore, if a query result object needs to be traversed into a dictionary every time, it is the same as flask.

If the GET request is not a request with content, the request received from the front-end is in JSON format.
Each time, you need to extract the content from the request. Body in bytes format.
Decode is decoded into a JSON string and then loads is used as a dictionary that can be processed by python.
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Note:
Return jsonresponse (book_list, safe = false)

Safe description, the book_list we passed in is a list format. In front-end JSON, {} format is supported, and [] format is also supported. However, Django considers that the JSON format of [] is insecure and will be verified. option to disable false, []

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Serialization: traverses the query results, converts them to a dictionary, and returns the jsonresponse
Deserialization: the front-end JSON is processed into a dictionary and then verified.
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1. Build a DRF framework project based on Django
Install DRF: Pip install djangorestframework
Register DRF: installed_apps = ['rest _ framework',]
Create a serializers. py in the sub-application to execute serialization and deserialization.
In Views, Class View uses the serializer to write the address in URLs.
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2. serializer

Definition: in fact, modelserializer is a subclass of serializer. It is more convenient to create a serializer with model classes. The actual serializer is as follows:
Class bookinfoserializer (serializers. serializer): Actually inherits serializer
"Book data serializer" serializer: serialization and deserialization
Id = serializers. integerfield (Label = 'id', read_only = true) read_only
Btitle = serializers. charfield (Label = 'name', max_length = 20)
Bpub_date = serializers. datefield (Label = 'publication date', required = false)
Bread = serializers. integerfield (Label = 'reading', required = false)
Bcomment = serializers. integerfield (Label = 'comments', required = false)
Image = serializers. imagefield (Label = 'image', required = false)

Field: similar to the creation of model classes. For specific fields, see handouts and common parameters (constraints)

Use: Create the object serializer = serializer (instance = none, Data = empty, ** kwarg)
Description: During serialization, model objects are passed into the instance parameter instance = serialized object.
During deserialization, the data to be deserialized is passed into the data parameter data = deserialization object.
You can use the context parameter to add additional data, that is, ** kwarg: context = {'request': Request} can be obtained through the context attribute of the serializer object.
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3. serialization operation: the process of constructing a dictionary is traversed after an object is queried, and jsonresponse is executed by the built-in Renderer.

3-1. serialization only uses the first parameter instance of the serializer object
Serializer = bookinfoserializer (instance = book)
The serialized data can be obtained through the data attribute. This data is not the same as the second parameter.
Serializer. Data

{'Id': 2, 'btitle': 'tianlong Babu ', 'bpub _ date': '2017-07-24', 'bread': 36, 'bcomment': 40, 'image': None}

3-2. If you want to serialize a query set queryset that contains multiple pieces of data, add the Limit = true parameter.
Book_qs = bookinfo. Objects. All ()
Serializer = bookinfoserializer (book_qs, bytes = true)
Serializer. Data
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4. nested serialization of correlated objects (hbook method adopted by hero-> book)

4-1.hbook is a foreign key: primarykeyrelatedfield
Hbook = serializers. primarykeyrelatedfield (Label = 'book', read_only = true)
Because it is a foreign key, the second location must have read_only = true or the query set queryset = bookinfo. Objects. All () does not report an error
When serializer. Data is serialized, the result is the primary key of the associated object {'hbook': 2}, that is, Book. Id.

4-2. Because the ID is not intuitive, change the foreign key field to stringrelatedfield for the detailed content string.
Hbook = serializers. stringrelatedfield (Label = 'book ')
Result: {'hbook': 'tianlong Babu '}

4-3. interface link: hyper‑relatedfield
Hbook = serializers. hyper1_relatedfield (Label = 'book', read_only = true, view_name = 'books-detail ')
You must specify the view_name parameter so that DRF can search for routes based on The View name and splice them into a complete URL. What is this view_name? One parameter in the URL is a namespace and associated with it.
Result: {'hbook': 'http: // 127.0.0.1: 8000/books/2 /'}

4-4. Associate the specified field data of the object: slugrelatedfield
Hbook = serializers. slugrelatedfield (Label = 'book', read_only = true, slug_field = 'bpub _ date ')
Slug_field specifies the field of the associated object
Result: {'hbook': datetime. Date (1986, 7, 24 )}

4-5. Use the serializer of the correlated object: serialize all contents of the book directly.
Hbook = bookinfoserializer ()
Result: {'hbook': ordereddict ([('id', 2), ('btitle', 'tianlongbabu ') te', '2017-07-24 '), ('bread', 36), ('bcomment', 40), ('image', none)])}

Understanding of serializer