Winerva Blog

current in process record the version will be update += 1, so when in the same time another one do same thing will updated_rows == 0.

when select task by id, the database lock the record. if other one to do same time the second one will get the “Task is already claimed or completed”

We use transaction.atomic() as a context manager to ensure that all database operations within the block are atomic, meaning they are either all committed or all rolled back in case of an error.

• Understanding Django Views
  • avoid add business logic into the view, if embedding business logic directly into the view will make it nonreusable, not testability and coupling.
• Django’s Generic Views
  • from django.views.generic import ListView, DetailView, TemplateView
  • from django.views.generic.dates import ArchiveIndexView, YearArchiveView, MonthArchiveView, DayArchiveView, TodayArchiveView, DateDetailView
  • from django.views.generic.edit import FormView, CreateView, DeleteView, UpdateView, DeleteView
  • use help(ListView) to check detail property and method and so on

• Mixins
  • refers to a class that provides additional functionality to other classes through inheritance.

• Django Mixin
  • ContextMixin: Adds extra context data to the view
  • TemplateResponseMixin: Renders template and returns an HTTP response
  • FormMixin: Used to handle form submission and validation
  • CreateModelMixin: Used to save a new object to database
  • UpdateModelMixin: Used to upate an existing object in database
  • DeleteModelMixin: Used to delete an object
• URL Configuration
  • ulrpatterns = [ re_path(r’^tasks/(?P<by_date>[0-9]{4}-[0-9]{2}-[0-9]{2})/$’, views.query_by_date, name=”task_list”),]

^: indicating the begin

$: indicateing the last

[0-9]{4}: 4 characters and each character is 0~9.

(?P<by_date>…….), will pass the value as by_date parameter to the view.

r preceding the string is a flag, informing Python that this is a raw string

• url path built-in convert:
  • str
  • int
  • slug
  • uuid
  • path
• url path custom convert

• URL Namespace and Name tasks:task-detail

to use namespace for urls, use app_name in the urls.py

• HttpRequest object
  • request.method
  • request.user
  • request.path
  • request.GET
  • request.POST
  • request.FIELS
  • request.headers

• HttpResponse object
  • the object accept a parameter that contains the content destined for client.