Django (四) 資料庫與模型使用

$ apt install mysql-server
$ apt install python3-dev libmysqlclient-dev
$ mysql_secure_installation

$ pip install mysqlclient

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': '資料庫名稱',
        'USER': '連接的帳號',
        'PASSWORD': '密碼',
        'HOST': 'IP位置',
        'PORT': 'Port值',
        'OPTIONs': {
            'init_command': "SET sql_mode='STRICT_TRANS_TABLES'",
        },
    }
}

$ python manage.py makemigrations #產生 class 描述檔案，位置在 app/migrations 中
$ python manage.py migrate #根據描述檔來變更資料庫設定

from <your_app> import models

admin.site.register(models.<your_class>)
...

posts = Post.objects.all() #取得此物件全部元素

from django.db import models

class User(models.Model):
    name = models.CharField(max_length=20)
    nickname = models.CharField(max_length=20)
    password = models.CharField(max_length=20)

    def __str__(self):
        return self.name

class Tag(models.Model):
    name = models.CharField(max_length=20)
    
    def __str__(self):
        return self.name

class Post(models.Model):
    Categories = [
        ('Life', '生活'),
        ('Travel', '旅遊'),
        ('Office', '職場'),
        ('Sport', '運動'),
        ('Tech', '科技'),
        ('Other', '其他')
    ]
    author = models.ForeignKey(User, on_delete=models.CASCADE)
    title = models.CharField(max_length=100)
    slug = models.SlugField(max_length=100, unique=True, allow_unicode=True)
    image = models.ImageField(blank=True, default='default.jpg')
    content = models.TextField(blank=True)
    category = models.CharField(max_length=10, choices=Categories)
    tags = models.ManyToManyField(Tag)
    date = models.DateTimeField(auto_now_add=True)
    
    class Meta:
        ordering = ('-date',)

    def __str__(self):
        return "({}) {}".format(self.author, self.title)

class Comment(models.Model):
     author = models.ForeignKey(User, on_delete=models.CASCADE)
     post = models.ForeignKey(Post, on_delete=models.CASCADE)
     content = models.TextField(blank=True)
     date = models.DateTimeField(auto_now=True)

     def __str__(self):
        return "({}) comment on {}".format(self.author, self.post)

MEDIA_URL = '/media/'
MEDIA_ROOT = BASE_DIR / 'media'

$ pip install Pillow

from django.contrib import admin
from blog import models

class PostAdmin(admin.ModelAdmin):
    list_display = ('title','author','category','date')
    ordering = ('-date',)

admin.site.register(models.User)
admin.site.register(models.Tag)
admin.site.register(models.Post, PostAdmin)
admin.site.register(models.Comment)

$ python manage.py makemigrations
$ python manage.py migrate

You are trying to add a non-nullable field 'Author' to post without a default; we can't do that (the database needs something to populate existing rows).
Please select a fix:
 1) Provide a one-off default now (will be set on all existing rows with a null value for this column)
 2) Quit, and let me add a default in models.py

<!-- index.html -->
{% extends 'base.html' %}
{% block title %} 首頁 {% endblock %}
{% block sidebar %} 
{% include 'sidebar1.html' %}
{% endblock %}
{% block content %}
{% for post in posts %}
<div class='card'>
    <div class="row g-0">
        <div class="col-md-4">
            <img src="{{ post.image.url }}" class="img-fluid rounded">
		</div>
        <div class="col-md-8">
            <div class='card-header fs-5 fw-bold'>
                <div class="row">
                    <div class="col-md-8">
                        <a href='/post/{{ post.slug }}' class="link-secondary">{{ post.title }}</a>
                    </div>
                    <div class="col-md-4">
                        <div class="text-end text-secondary fs-6 pt-1">
                            作者：{{ post.author.nickname }}
                        </div>
                    </div>
                </div>   
            </div>
            <div class='card-body'>
                <p class="card-text">{{ post.content | truncatechars:100 }}</p>
                <p class="card-text">
                    <small class='text-muted'>發布時間：{{ post.date | date:"Y M d, H:i"}}</small>
                </p>
            </div>
        </div>
    </div>
</div>
<br>
{% endfor %}
{% endblock %}

<!-- post.html -->
{% extends 'base.html' %}
{% block title %} 文章閱覽 {% endblock %}
{% block sidebar %} 
{% include 'sidebar1.html' %}
{% endblock %}
{% block content %}
<div class='card'>
    <div class='card-header fs-5 fw-bold'>
            {{ post.title }}
    </div>
    <div class='card-body'>
            {{ post.content | linebreaks }}
    </div>
    <div class='card-footer text-muted'>
        <small>發布時間：{{ post.date | date:"Y M d, H:i"}}</small>
    </div>
</div>
<br>
<div class="card">
    <div class="card-header fs-5 fw-bold">
        留言
    </div>
    <div class='card-body'>
        {% if comments %}
        {% for comment in comments %} 
        <div class='card'>
            <div class="card-body">
                <h5>{{ comment.author.nickname }}</h5>
                <p>{{ comment.content }}</p>
                <small>發布時間：{{ comment.date | date:"Y M d, H:i"}}</small>
            </div>
        </div>
        <br>
        {% endfor %}
        {% else %}
            <p>目前還沒有人留言喔！</p>
        {% endif %}
    </div>
</div>
<br>
<a href='/' class='link-secondary ms-2 pb-4'>回首頁</a>
{% endblock %}

from django.shortcuts import render, redirect
from django.http import HttpResponse
from .models import User, Tag, Post, Comment

def index(request):
    posts = Post.objects.all()
    return render(request, 'index.html', locals())

def showpost(request, slug):
    posts = Post.objects.all()
    try:
        post = Post.objects.get(slug=slug)   
        if post != None:
            comments = Comment.objects.filter(post=post)
            return render(request, 'post.html', locals())
    except:
        return redirect('/')

from django.conf.urls.static import static
from django.conf import settings

...

urlpatterns += static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)