BooleanField – Django 模型

BooleanField 是一个真/假字段。它就像 C/C++ 中的布尔字段。此字段的默认表单小部件是 CheckboxInput，如果 null=True，则为 NullBooleanSelect。当未定义 Field.default 时，BooleanField 的默认值为 None。通过同时将默认属性设置为真/假，可以将默认值定义为真或假。

句法：

field_name = models.BooleanField(**options)

Django Model Boolean字段说明

使用示例说明 BooleanField。考虑一个名为 geeksforgeeks 的项目，它有一个名为 geeks 的应用程序。

Refer to the following articles to check how to create a project and an app in Django. 

• How to Create a Basic Project using MVT in Django?
• How to Create an App in Django ?

在极客应用的models.py文件中输入以下代码。

Python3

from django.db import models
from django.db.models import Model
# Create your models here.
 
class GeeksModel(Model):
    geeks_field = models.BooleanField()

将极客应用添加到 INSTALLED_APPS

Python3

# Application definition
 
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'geeks',
]

现在，当我们从终端运行 makemigrations 命令时，

Python manage.py makemigrations

将在 geeks 目录中创建一个名为 migrations 的新文件夹，其中包含一个名为 0001_initial.py 的文件

Python3

# Generated by Django 2.2.5 on 2019-09-25 06:00
 
from django.db import migrations, models
 
class Migration(migrations.Migration):
 
    initial = True
 
    dependencies = [
    ]
 
    operations = [
        migrations.CreateModel(
            name ='GeeksModel',
            fields =[
                ('id',
                  models.AutoField(auto_created = True,
                  primary_key = True,
                  serialize = False,
                  verbose_name ='ID'
                )),
                ('geeks_field', models.BooleanField()),
            ],
        ),
    ]

现在运行，

Python manage.py migrate

因此，当您在项目上运行迁移时，会创建一个 geeks_field BooleanField 。它是一个存储布尔值的字段——真/假。

如何使用布尔字段？

BooleanField 用于检查特定条件，例如检查用户的电子邮件是否经过验证。可以使用 BooleanField 将其标记为 True 或 False。我们还可以使用 default=True 将其设置为 False。

Python3

# importing the model
# from geeks app
from geeks.models import GeeksModel
 
# creating a instance of
# GeeksModel
geek_object = GeeksModel.objects.create(geeks_field = True)
geek_object.save()

现在让我们在管理服务器中检查它。我们已经创建了 GeeksModel 的一个实例。

字段选项

字段选项是赋予每个字段的参数，用于应用某些约束或将特定特征赋予特定字段。例如，向 BooleanField 添加参数 null = True 将使其能够将该表的空值存储在关系数据库中。
以下是 BooleanField 可以使用的字段选项和属性。

Field Options	Description
Null	If True, Django will store empty values as NULL in the database. Default is False.
Blank	If True, the field is allowed to be blank. Default is False.
db_column	The name of the database column to use for this field. If this isn’t given, Django will use the field’s name.
db_index	If True, a database index will be created for this field.
db_tablespace	The name of the database tablespace to use for this field’s index, if this field is indexed. The default is the project’s DEFAULT_INDEX_TABLESPACE setting, if set, or the db_tablespace of the model, if any. If the backend doesn’t support tablespaces for indexes, this option is ignored.
Default	The default value for the field. This can be a value or a callable object. If callable it will be called every time a new object is created.
help_text	Extra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form.
primary_key	If True, this field is the primary key for the model.
editable	If False, the field will not be displayed in the admin or any other ModelForm. They are also skipped during model validation. Default is True.
error_messages	The error_messages argument lets you override the default messages that the field will raise. Pass in a dictionary with keys matching the error messages you want to override.
help_text	Extra “help” text to be displayed with the form widget. It’s useful for documentation even if your field isn’t used on a form.
verbose_name	A human-readable name for the field. If the verbose name isn’t given, Django will automatically create it using the field’s attribute name, converting underscores to spaces.
validators	A list of validators to run for this field. See the validators documentation for more information.
Unique	If True, this field must be unique throughout the table.