代码之家 › 专栏 › 技术社区 › aalberti333

Django中使用JSONField的默认dict列表

django-rest-framework django python

aalberti333 · 技术社区 · 6 年前

Django 2.0、Django Rest Framework 3.8、Python 3.6

我正在使用Postgres数据库,并尝试将以下内容设置为JSONField的默认值:

from django.db import models
from django.contrib.postgres.fields import JSONField

class TrainerProfile(models.Model):
    """data required to pull up trainer profile"""

    specific_workouts = JSONField(default=[{"specific": "standard session", "price": 100.00, "units": 1, "hours_per_unit": 1}, {"specific": "standard session", "price": 250.00, "units": 3, "hours_per_unit": 1}, {"specific": "standard session", "price": 300.00, "units": 5, "hours_per_unit": 1}])

    def __str__(self):
        return str(self.specific_workouts)

从Django文档中可以看到:

如果给字段一个默认值,请确保它是可调用的,例如dict (对于空的默认值)或返回dict的callable(例如函数)。错误地使用default={}会创建一个可变的默认值

我想提供一份清单包含

"specific_workouts": [
            {
                "price": 100.0,
                "units": 1,
                "specific": "standard session",
                "hours_per_unit": 1
            },
            {
                "price": 250.0,
                "units": 3,
                "specific": "standard session",
                "hours_per_unit": 1
            },
            {
                "price": 300.0,
                "units": 5,
                "specific": "standard session",
                "hours_per_unit": 1
            }
        ]

我想我得重写了 save() 但我不知道该如何实现。非常感谢您的帮助。

更新

from django.db import models
from django.contrib.postgres.fields import JSONField

def default_specific_workouts():
    return [
        {
            "price": 100.0,
            "units": 1,
            "specific": "standard session",
            "hours_per_unit": 1
        },
        {
            "price": 250.0,
            "units": 3,
            "specific": "standard session",
            "hours_per_unit": 1
        },
        {
            "price": 300.0,
            "units": 5,
            "specific": "standard session",
            "hours_per_unit": 1
        }
    ]

class TrainerProfile(models.Model):
    """data required to pull up trainer profile"""

    specific_workouts = JSONField(default=default_specific_workouts)

    def __str__(self):
        return str(self.specific_workouts)

也值得一提 即使我输入:

specific_workouts = JSONField(default=list)

specific_workouts = JSONField(default=dict)

1 回复 | 直到 6 年前

MrName 6 年前

如您引用的摘录所述,您可以使用任何callable作为默认值。因此,您可以创建自己的方法来调用以创建默认值。

def default_specific_workouts():
    # You probably want this in a variable, just copy/pasting your sample data
    # to keep the example simple
    return [
        {
            "price": 100.0,
            "units": 1,
            "specific": "standard session",
            "hours_per_unit": 1
        },
        {
            "price": 250.0,
            "units": 3,
            "specific": "standard session",
            "hours_per_unit": 1
        },
        {
            "price": 300.0,
            "units": 5,
            "specific": "standard session",
            "hours_per_unit": 1
        }
    ]

现在您可以这样做:

specific_workouts = JSONField(default=default_specific_workouts)