django-m2m-history 0.3.6

Django ManyToMany历史
========================

[](http://badge.fury.io/py/django-m2m-history) [](https://travis-ci.org/ramusus/django-m2m-history) [](https://coveralls.io/r/ramusus/django-m2m-history)

Django ManyToMany关系字段变更历史。与通常的Django的ManyToManyField一样，它生成中间连接表
来表示多对多关系，但有两个额外的列：'time_from'和'time_to'。使用字段的更新接口，可以检索此字段值的所有版本的
历史。

兼容性
-------------

* python v2.7, v3.4
* django >=1.5, <=1.8. **与Django 1.9不兼容**
* postgres

安装
------------

pip install django-m2m-history

将以下行添加到`settings.py`中

INSTALLED_APPS = (
...
'm2m_history',
)

用法示例
-------------

创建2个具有多对多关系的模型

class Publication(models.Model)
title = models.CharField(max_length=30)

def __str__(self)
return self.title

class Article(models.Model)
headline = models.CharField(max_length=100)
publications = ManyToManyHistoryField(Publication)

def __str__(self)
return self.headline

创建对象并在它们之间建立关系

>>> p1 = Publication.objects.create(title='Pub1')
>>> p2 = Publication.objects.create(title='Pub2')
>>> p3 = Publication.objects.create(title='Pub3')

>>> article = Article.objects.create(headline='Article1')
>>> state_time1 = datetime.now()

>>> article.publications = [p1, p2]
>>> state_time2 = article.publications.last_update_time()
>>> article.publications.all()
[<Publication: Pub1>, <Publication: Pub2>]
>>> article.publications.count()
2
>> article.publications.through.objects.count()
2

>> article.publications = [p3]
>> state_time3 = article.publications.last_update_time()
>>> article.publications.all()
[[出版物: Pub3]]
>>> article.publications.count()
1
>> article.publications.through.objects.count()
3

>> article.publications.add(p2, p1)
>> state_time4 = article.publications.last_update_time()
>>> article.publications.all()
[[出版物: Pub1], [出版物: Pub2], [出版物: Pub3]]
>>> article.publications.count()
3
>> article.publications.through.objects.count()
5

>> article.publications.remove(p2, p1)
>> state_time5 = article.publications.last_update_time()
>>> article.publications.all()
[[出版物: Pub3]]
>>> article.publications.count()
1
>> article.publications.through.objects.count()
5

>>> article.publications = [p1, p2]
>> state_time6 = article.publications.last_update_time()
>>> article.publications.all()
[<Publication: Pub1>, <Publication: Pub2>]
>>> article.publications.count()
2
>> article.publications.through.objects.count()
7

>> article.publications.clear()
>> state_time7 = article.publications.last_update_time()
>>> article.publications.all()
[]
>>> article.publications.count()
0
>> article.publications.through.objects.count()
7

通过时间戳获取历史状态对象

>> article.publications.were_at(state_time1)
[]

>> article.publications.were_at(state_time2)
[<Publication: Pub1>, <Publication: Pub2>]

>> article.publications.were_at(state_time3)
[[出版物: Pub3]]

>> article.publications.were_at(state_time4)
[[出版物: Pub1], [出版物: Pub2], [出版物: Pub3]]

>> article.publications.were_at(state_time5)
[[出版物: Pub3]]

>> article.publications.were_at(state_time6)
[<Publication: Pub1>, <Publication: Pub2>]

>> article.publications.were_at(state_time7)
[]

通过时间戳获取历史状态中添加和删除的对象

>> article.publications.added_at(state_time3)
[[出版物: Pub3]]

>> article.publications.removed_at(state_time3)
[<Publication: Pub1>, <Publication: Pub2>]

>> article.publications.added_at(state_time4)
[<Publication: Pub1>, <Publication: Pub2>]

>> article.publications.removed_at(state_time5)
[<Publication: Pub1>, <Publication: Pub2>]

>> article.publications.added_at(state_time6)
[<Publication: Pub1>, <Publication: Pub2>]

>> article.publications.removed_at(state_time6)
[[出版物: Pub3]]