Finished django app, part 2

.gitignore

@@ -1,3 +1,4 @@
 .vscode
 **__pycache__**
 **db.sqlite3**
+**/migrations**

first_django_app.md

@@ -5,7 +5,13 @@ Target: create a basic poll application, with 2 parts a **public site** and a **
 * **public site**: let's pp view polls and vote
 * **admin site**: let's you(admin) add/change/delete poll
 
-## Creating a project
+## Part 1
+
+1. Create web project
+2. Create 1st app
+3. Create 1st view
+4. Add view & app into web url
+### Creating a project
 
 In the source directory, create project by
 
@@ -39,7 +45,7 @@ Explain file structure:
 * `mysite/asgi.py`: An entry-point for ASGI-compatible webservers
 * `mysite/wsgi.py`: Entry-point for WSGI-compatible webservers
 
-## The development server
+### The development server
 
 Start server steps:
 1. cd into outer `mysite/` dir
@@ -50,7 +56,7 @@ Outcome:
 * A development server is started. So no need to config a production server (e.g. Apache)
 * Note: don't use it as production environment.
 
-## Creating the Polls app
+### Creating the Polls app
 
 > Projects vs. apps
 > 
@@ -76,9 +82,9 @@ polls/
     views.py
 ```
 
-## Write the first view
+### Write the first view
 
-### Step 1: Create a simple view of `polls` app
+#### Step 1: Create a simple view of `polls` app
 
 modify `polls/views.py` as
 
@@ -92,7 +98,7 @@ def index(request):
 
 * `def index(request):...` is the simplest view
 
-### Step 2: In `polls` app, map the URL to this view
+#### Step 2: In `polls` app, map the URL to this view
 
 After creating a view, map it to a URL so we can call it. Create `polls/urls.py`, and setup mapping `urlpatterns`
 
@@ -106,7 +112,7 @@ urlpatterns = [
 ]
 ```
 
-### Step 3: Point the root URLconf for polls
+#### Step 3: Point the root URLconf for polls
 
 To point the root URLconf at `polls.urls` module:
 1. In `mysite/urls.py`
@@ -125,14 +131,14 @@ urlpatterns = [
 ]
 ```
 
-#### django.urls.include()
+##### django.urls.include()
 
 > django.urls.include(): A function that takes a full Python import path to another URLconf module that should be “included” in this place.
 
 * new imported `include()` function allows referencing other URLconfs.
 * `'polls.urls'` is the package that we are using, hence `mysite` can connect to `polls` app
 
-#### path()
+##### path()
 
 Here `path()` function is passed **route** and **view**; two additional option available **kwargs**, and **name**
 
@@ -141,5 +147,29 @@ Here `path()` function is passed **route** and **view**; two additional option a
 * `path()` argument **kwargs**: passed in a dictionary to the target view
 * `path()` argument **name**: naming URL, so we can refer to it elsewhere.
 
-## Database setup
+## Part 2
 
+### Database setup
+
+1. Modify `mysite/settings.py` for database binding
+2. `python manage.py migrate` create database for each app
+
+### Models Creation
+
+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
+
+### Activate Models
+
+改变模型需要这三步：
+
+* 编辑 models.py 文件，改变模型
+* 运行 python manage.py makemigrations 为模型的改变生成迁移文件。
+* 运行 python manage.py migrate 来应用数据库迁移。
+
+在这之前，确认polls已经在 INSTALLED_APPS的settings中。
+
+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/)
+
+### Test API
+
+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/)

src/mysite/settings.py

@@ -37,6 +37,7 @@ INSTALLED_APPS = [
     'django.contrib.sessions',
     'django.contrib.messages',
     'django.contrib.staticfiles',
+    'polls.apps.PollsConfig',
 ]
 
 MIDDLEWARE = [

src/polls/admin.py

@@ -1,3 +1,4 @@
 from django.contrib import admin
 
-# Register your models here.
+from .models import Question
+admin.site.register(Question)

src/polls/models.py

@@ -1,3 +1,24 @@
-from django.db import models
+import datetime
 
-# Create your models here.
+from django.db import models
+from django.utils import timezone as djtz
+
+class Question(models.Model):
+    # question_text & pub_date are instances of field
+    question_text = models.CharField(max_length=200)
+    pub_date = models.DateTimeField('date published')
+
+    def was_published_recently(self):
+        return self.pub_date >= djtz.now() - datetime.timedelta(days=1)
+
+    def __str__(self) -> str:
+        return self.question_text
+
+class Choice(models.Model):
+    # ForeinKey to define a relationship, here tells Choice object is mapped to a Question
+    question = models.ForeignKey(Question, on_delete=models.CASCADE)
+    choice_text = models.CharField(max_length=200)
+    votes = models.IntegerField(default=0)
+
+    def __str__(self) -> str:
+        return self.choice_text