django model
首先对于一个习惯用django model的骚年来说,你肯定对django model自定制用的很熟悉,但突然让你用django dynamic model,也许会有很多人懵逼,然后各种查官网,看论坛,翻源码,终于搞出了。不过对于我们这些新手来说是相当吃力的。现在整理出来方便日后观看。
对于什么是django model 的定义就不多说
create table
在动态创建之前,应该先了解一下makemigrations以及migrate 的源码,先看看他们是如何生成的。下面是自己测试成功代码,仅供参考
from django.db import connection, migrations, models from django.db.migrations.executor import MigrationExecutor def create_table(table_name, model_fields, app_label): class Migration(migrations.Migration): initial = True dependencies = [] operations = [ migrations.CreateModel( name=‘a‘, fields=[ (‘title‘, models.CharField(choices=[(‘MR‘, ‘Mr.‘), (‘MRS‘, ‘Mrs.‘), (‘MS‘, ‘Ms.‘)], max_length=3)), (‘birth_date‘, models.DateField(blank=True, null=True)), ], ), migrations.CreateModel( name=‘b‘, fields=[ (‘id‘, models.AutoField(auto_created=True, serialize=False, verbose_name=‘ID‘)), (‘name‘, models.CharField(max_length=100)), (‘authors‘, models.ManyToManyField(to=‘app.a‘, related_name=‘author‘)), ], ), migrations.CreateModel( name=‘c‘, fields=[ (‘id‘, models.AutoField(auto_created=True, serialize=False, verbose_name=‘ID‘)), (‘name‘, models.CharField(max_length=32)), (‘data‘, models.CharField(db_index=True, max_length=32)), ], ), ] executor = MigrationExecutor(connection) migration = Migration(table_name, app_label) with connection.schema_editor(atomic=True) as schema_editor: migration.apply(executor._create_project_state(), schema_editor)
执行代码
custom_model = create_table(‘example‘, fields, app_label=‘app‘, )
注意 fields可自定制
执行成功后,你会发现你的数据表里多了这几个表
此时可不能万事大吉,怎么去操作也是很重要的。
操作danamic model
def get_model(name, fields=None, app_label=None, module=‘‘, options=None, admin_opts=None): """ Create specified model """ class Meta: db_table = name if app_label: setattr(Meta, ‘app_label‘, app_label) if options is not None: for key, value in options.items(): setattr(Meta, key, value) attrs = {‘__module__‘: module, ‘Meta‘: Meta} if fields: attrs.update(fields) model = type(name, (models.Model,), attrs) return model
执行 get_model
al = dict( title=models.CharField(choices=[(‘MR‘, ‘Mr.‘), (‘MRS‘, ‘Mrs.‘), (‘MS‘, ‘Ms.‘)], max_length=3), birth_date=models.DateField(blank=True, null=True) ) model_a = get_model(‘app_a‘, app_label=‘app‘, fields=al)
注意此时al 为你动态创建的model 字段,此时你获取该model时需要将字段传进去
而这此时也只是对单表操作,如果遇到manytomany呢?
那么别急,肯定会有解决的办法
哈哈
model_a = get_model(‘app_a‘, app_label=‘app‘, fields=al) fields = dict( name=models.CharField(max_length=100), authors=model_a ) modelb = get_model(‘app_b‘, app_label=‘app‘, fields=fields) obj = modelb.objects.filter(id=1).first() print(obj) a = obj.authors.objects.values(‘title‘) print(a)
即:如果你要正向操作,针对上面创建得表,你首先创建a表的类型,然后将a类型作为authors的参数传进去即可。
现在就一切OK了,
原文地址:https://www.cnblogs.com/flash55/p/9064241.html
时间: 2024-10-09 05:48:39