175 lines
5.2 KiB
Markdown
175 lines
5.2 KiB
Markdown
# First Django App
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Target: create a basic poll application, with 2 parts a **public site** and a **admin site**
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* **public site**: let's pp view polls and vote
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* **admin site**: let's you(admin) add/change/delete poll
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## Part 1
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1. Create web project
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2. Create 1st app
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3. Create 1st view
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4. Add view & app into web url
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### Creating a project
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In the source directory, create project by
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```
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$ django-admin startproject <project_name>
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```
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Constraint on `<project_name>`:
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* don't use names that conflict with django
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* e.g. `django`, `test` (test with built-in test file)
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```
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mysite/
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manage.py
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mysite/
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__init__.py
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settings.py
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urls.py
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asgi.py
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wsgi.py
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```
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Explain file structure:
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* top-level `mysite/`: container of the project, can be renamed latter w/o affect Django framework
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* `manage.py`: cmd-line utility let us to interact (admin) with Django projects.
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* inner `mysite/` dir: actual Python package for the project.
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* Importing any package from here: e.g. `mysite.urls`
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* `mysite/__init__.py`: empty file, tell python start from here.
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* `mysite/settings.py`: settings/config for this django project.
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* `mysite/urls.py`: URL declarations for this Django pjt; a "table of contents" of this Django website.
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* `mysite/asgi.py`: An entry-point for ASGI-compatible webservers
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* `mysite/wsgi.py`: Entry-point for WSGI-compatible webservers
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### The development server
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Start server steps:
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1. cd into outer `mysite/` dir
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2. Start server via: `python manage.py runserver`
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Outcome:
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* A development server is started. So no need to config a production server (e.g. Apache)
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* Note: don't use it as production environment.
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### Creating the Polls app
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> Projects vs. apps
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>
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> What’s the difference between a project and an app? An app is a Web application that does something – e.g., a Weblog system, a database of public records or a small poll app. A project is a collection of configuration and apps for a particular website. A project can contain multiple apps. An app can be in multiple projects.
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Create a poll app along `mysite/`. For what?
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```
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$ python manage.py startapp polls
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```
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app hierarchy
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```
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polls/
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__init__.py
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admin.py
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apps.py
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migrations/
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__init__.py
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models.py
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tests.py
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views.py
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```
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### Write the first view
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#### Step 1: Create a simple view of `polls` app
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modify `polls/views.py` as
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```python
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from django.http import request
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from django.shortcuts import render
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def index(request):
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return HttpResponse("Hello, world. You're at the polls index")
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```
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* `def index(request):...` is the simplest view
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#### Step 2: In `polls` app, map the URL to this view
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After creating a view, map it to a URL so we can call it. Create `polls/urls.py`, and setup mapping `urlpatterns`
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```python
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from django.urls import path
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from . import views
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urlpatterns = [
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path('', views.index, name='index'),
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]
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```
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#### Step 3: Point the root URLconf for polls
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To point the root URLconf at `polls.urls` module:
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1. In `mysite/urls.py`
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1. add import for `django.urls.inclue`
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2. insert a `include()` in `urlpatterns` list
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i.e.
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```python
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from django.contrib import admin
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from django.urls import include, path
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urlpatterns = [
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path('polls/', include('polls.urls')),
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path('admin/', admin.site.urls),
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]
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```
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##### django.urls.include()
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> django.urls.include(): A function that takes a full Python import path to another URLconf module that should be “included” in this place.
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* new imported `include()` function allows referencing other URLconfs.
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* `'polls.urls'` is the package that we are using, hence `mysite` can connect to `polls` app
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##### path()
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Here `path()` function is passed **route** and **view**; two additional option available **kwargs**, and **name**
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* `path()` argument **route**: a string that contains a URL pattern. When Django processing a request, it starts at the first pattern in `urlpatterns` and go down the list, comparing requested URL against each pattern
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* `path()` argument **view**: when Django finds a matching pattern, it calls specified view function (a `HttpRequest` obj as the 1st argument, and others captured values as keyword argument)
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* `path()` argument **kwargs**: passed in a dictionary to the target view
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* `path()` argument **name**: naming URL, so we can refer to it elsewhere.
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## Part 2
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### Database setup
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1. Modify `mysite/settings.py` for database binding
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2. `python manage.py migrate` create database for each app
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### Models Creation
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在 Django 里写一个数据库驱动的 Web 应用的第一步: **定义模型** - 也就是数据库结构设计和附加的其它元数据 Meta Data
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### Activate Models
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改变模型需要这三步：
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* 编辑 models.py 文件，改变模型
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* 运行 python manage.py makemigrations 为模型的改变生成迁移文件。
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* 运行 python manage.py migrate 来应用数据库迁移。
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在这之前，确认polls已经在 INSTALLED_APPS的settings中。
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详情如何使用 `manage.py` 可check [Django后台文档](https://docs.djangoproject.com/zh-hans/3.1/ref/django-admin/)
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### Test API
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进入 `python manage.py shell` 可以使用Django创建的各种API，如[数据库抽象API database API(建议细看)](https://docs.djangoproject.com/zh-hans/3.1/topics/db/queries/) |