django开发(二)

1.django数据库操作---model的使用以及django自带的数据api

django中已经做了ORM，表就是一个类class，表中的一个项就是一个对象object，很好用

1.1django自动把每次你对数据库的操作（更改）看成了对model的改变，然后你生成迁移文件，执行迁移更改，使你专注与django而不是sql

上面第一步和第二部之间还要加上一步激活模型，即把model.py所在的app模块注册到settings.py中的installed_app中，体现了可插拔的应用哲学

1.2常用命令

python manage.py makemigrations app_name
创建迁移文件


python manage.py sqlmigrate app_name 0001
0001是是生成的迁移文件名称，可能需要修改
查看生成的迁移文件，也就是查看准备执行什么sql语句


python manage.py migrate
执行迁移

 1.3数据库的shell操作（非常好用）

django的shell进行了ORM很好用，而且数据库中的每一个数据项在django中不仅是一个数据项，他还被映射成一个独立的对象，他还能被加入类方法

ORM-object relation mapping

python manage.py shell
启动django的shell，自带的shell工具，可以很容易的对数据库进行crud操作，外键检索等等，非常好用，其进行了ORM

python manage.py dbshell
启动对应对应数据库的shell

 

>>> from polls.models import Choice, Question

# Make sure our __str__() addition worked.
>>> Question.objects.all()
<QuerySet [<Question: What's up?>]>

# Django provides a rich database lookup API that's entirely driven by
# keyword arguments.
>>> Question.objects.filter(id=1)
<QuerySet [<Question: What's up?>]>
>>> Question.objects.filter(question_text__startswith='What')
<QuerySet [<Question: What's up?>]>

# Get the question that was published this year.
>>> from django.utils import timezone
>>> current_year = timezone.now().year
>>> Question.objects.get(pub_date__year=current_year)
<Question: What's up?>

# Request an ID that doesn't exist, this will raise an exception.
>>> Question.objects.get(id=2)
Traceback (most recent call last):
    ...
DoesNotExist: Question matching query does not exist.

# Lookup by a primary key is the most common case, so Django provides a
# shortcut for primary-key exact lookups.
# The following is identical to Question.objects.get(id=1).
>>> Question.objects.get(pk=1)
<Question: What's up?>

# Make sure our custom method worked.
>>> q = Question.objects.get(pk=1)
>>> q.was_published_recently()
True

# Give the Question a couple of Choices. The create call constructs a new
# Choice object, does the INSERT statement, adds the choice to the set
# of available choices and returns the new Choice object. Django creates
# a set to hold the "other side" of a ForeignKey relation
# (e.g. a question's choice) which can be accessed via the API.
>>> q = Question.objects.get(pk=1)

# Display any choices from the related object set -- none so far.
>>> q.choice_set.all()
<QuerySet []>

# Create three choices.
>>> q.choice_set.create(choice_text='Not much', votes=0)
<Choice: Not much>
>>> q.choice_set.create(choice_text='The sky', votes=0)
<Choice: The sky>
>>> c = q.choice_set.create(choice_text='Just hacking again', votes=0)

# Choice objects have API access to their related Question objects.
>>> c.question
<Question: What's up?>

# And vice versa: Question objects get access to Choice objects.
>>> q.choice_set.all()
<QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>
>>> q.choice_set.count()
3

# The API automatically follows relationships as far as you need.
# Use double underscores to separate relationships.
# This works as many levels deep as you want; there's no limit.
# Find all Choices for any question whose pub_date is in this year
# (reusing the 'current_year' variable we created above).
>>> Choice.objects.filter(question__pub_date__year=current_year)
<QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>

# Let's delete one of the choices. Use delete() for that.
>>> c = q.choice_set.filter(choice_text__startswith='Just hacking')
>>> c.delete()

1.3常用的ORM之后的函数（在django中的shell运行）

class.objects.get()/filter(xxx__startwith='')/all()

q.choice_set.all()查找外键是q的所有对象

q.choice_set.count()对上一个计数

q.delete()

更多用法见文档

https://docs.djangoproject.com/zh-hans/2.1/ref/models/relations/

https://docs.djangoproject.com/zh-hans/2.1/topics/db/queries/#field-lookups-intro

https://docs.djangoproject.com/zh-hans/2.1/topics/db/queries/

2.django的后台管理页面功能

即在web页面中动态添加、修改、查看数据库中对象和数据，真的很方便很好用

2.1相关的一些命令

python manage.py createsuperuser
创建管理员账号
3 
4 http://127.0.0.1:8000/admin/
5 访问管理界面

2.2但是一定要注意，如果想管理某个app应用模块的model（也就是其中的数据表以及其映射的对象和类），一定要把本模块的model中的class注册到本app模块中的admin.py中

from django.contrib import admin
from .models import Question

admin.site.register(Question)

在本模块的admin.py中添加代码，将需要管理的数据库表注册到admin后台管理中去

2.3调整admin后台管理的显示顺序跟风格

from django.contrib import admin

from .models import Question


class QuestionAdmin(admin.ModelAdmin):
    fieldsets = [
        (None,               {'fields': ['question_text']}),
        ('Date information', {'fields': ['pub_date']}),
    ]

admin.site.register(Question, QuestionAdmin)

3.django中的测试

3.1django中的单元测试，在app模块中的test.py中写代码，注意方法名要以test开头，运行测试脚本时候的命令

python manage.py test app_name 

3.2如果在提交代码的时候自动化的进行测试，那也就是所谓的持续集成----continuous integration 

4.静态文件的查找

4.1静态文件目录一般为app_name/static/appname/[type]/xxx.xxx，然后使用 django.contrib.staticfiles 即可让django自动的去查找对应的静态文件，方便管理，但是要在app模块中

4.2django让app有自己的模板有自己的静态文件，再次体现了django的app为单一的模块的思想。但是如果想让django自己去找，那要先把模块注入进来

5.进阶版后台管理界面

5.1可以设置显示数据表class的字段顺序，显示外键、分组显示、还可以自定义admin界面风格等等，这些都是在对应的admin.py中写代码

https://docs.djangoproject.com/zh-hans/2.1/intro/tutorial07/

from django.contrib import admin
from .models import Choice, Question

class ChoiceInline(admin.StackedInline):
    model = Choice
    extra = 3


class QuestionAdmin(admin.ModelAdmin):
    fieldsets = [
        (None,               {'fields': ['question_text']}),
        ('Date information', {'fields': ['pub_date'], 'classes': ['collapse']}),
    ]
    inlines = [ChoiceInline]

admin.site.register(Question, QuestionAdmin)

json、dict、对象之间的互相转化