Django -- Models

from django.db import models

# Create your models here.
class Post(models.Model):
    title = models.CharField(max_length=140)       #Django会在表中自动添加字段： "id" integer NOT NULL PRIMARY KEY AUTOINCREMENT
    body = models.TextField()
    date = models.DateTimeField()

    def __str__(self):
        return self.title

1 makemigrations  blog    修改models后，创建新的migrations

2 migrate                 提交migrations，或者显示他们的状态

其他

sqlmigrate  blog  0001    显示某一个migration的SQL状态(创建table等操作)

showmigrations  列出project的所有migrations

from blog.models import Post

p = Post(1, ‘first blog‘, ‘This is my first blog.‘, ‘2016-04017‘)

p.save()

Post.objects.all()

#blog/urls.py

from django.conf.urls import url, include
from django.views.generic import ListView, DetailView     #使用通用视图
from blog.models import Post

urlpatterns = [
    url(r‘^$‘, ListView.as_view(queryset=Post.objects.all().order_by("-date")[:25]), template_name="blog/blog.html"),     

　　url(r‘^(?P<pk>\d+)$‘, DetailView.as_view(model=Post, template_name=‘blog/post.html‘)),       #(?P<name>pattern)

　　　　　　#<pk>:primary key，这里就是‘id‘，获得对象post=Post.objects.get(pk=\d+)并传入post.html中 

]   

#blog/templates/blog/blog.html

{% extends ‘blog/basic.html‘ %}

{% block content %}

    {% for post in object_list %}
        <h5>{{ post.date|date:‘Y-m-d‘ }}<a href=‘/blog/{{ post.id }}‘> {{ post.title }}</a></h5>
    {% endfor %}

{% endblock %} 

{% extends ‘blog/basic.html‘ %}



{% block content %}

<h3>{{ post.title }}</h3>

<h6>on {{ post.date }}</h6>

<p>{{ post.body | safe | linebreaks }}</p>     #safe模式：可以使用html标签，否则原型输出；   linebreaks 保持换行

{% endblock %}

class Album(models.Model):
    ...

class Song(models.Model):
    album = models.ForeignKey(Album, on_delete=models.CASCADE)
    ...

# Song是依赖于Album的，on_delete=models.CASCADE即当删除一个Album时，依赖它的Song也会一起删除
# 通过Album访问Song：  
    album = Album()   
    song = album.song_set.all()        .get() .filter .count() 
#通过Song访问Album：
    song = Song()
　　album = song.album.all()         get filter  count...