Question

我正在尝试将在一个类中计算的属性转换为另一个类。我被卡住了......

在“奖励”课程中，我需要从“pledge_level”中减去“deductible”。在“承诺”课程中，我需要从“金额”中减去“not_taxable”以返回“decuctible_total”。

在我的模板中访问它时可以正常工作：

(${{ reward.deductible}} is tax deductible or ${{ reward.not_taxable }} is not tax deductible)

在服务器上运行时，我收到内部服务器错误：[Django] ERROR（EXTERNAL IP）：内部服务器错误：/ projects / fund / billing / 1000

这是追溯：

Internal Server Error: /projects/fund/billing/1000/
Traceback (most recent call last):
File "/var/venv/website/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/var/sites/proj/payments/views.py", line 98, in pledge_billing
html = template.render(c)
File "/var/venv/website/lib/python2.7/site-packages/django/template/backends/django.py", line 74, in render
return self.template.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 209, in render
return self._render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 201, in _render
return self.nodelist.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 903, in render
bit = self.render_node(node, context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 917, in render_node
return node.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/loader_tags.py", line 135, in render
return compiled_parent._render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 201, in _render
return self.nodelist.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 903, in render
bit = self.render_node(node, context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 917, in render_node
return node.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/loader_tags.py", line 65, in render
result = block.nodelist.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 903, in render
bit = self.render_node(node, context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 917, in render_node
return node.render(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 957, in render
output = self.filter_expression.resolve(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 647, in resolve
obj = self.var.resolve(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 787, in resolve
value = self._resolve_lookup(context)
File "/var/venv/website/lib/python2.7/site-packages/django/template/base.py", line 825, in _resolve_lookup
current = getattr(current, bit)
File "/var/sites/proj/projects/models.py", line 81, in deductible_total
return self.get_deductible_total()
File "/var/sites/proj/projects/models.py", line 77, in get_deductible_total
return (self.amount - self.not_taxable)
AttributeError: 'Pledge' object has no attribute 'not_taxable'

models.py

class Pledge(models.Model):
    project = models.ForeignKey('Project')
    amount = models.DecimalField(decimal_places=2,max_digits=10,
        default=D('0.00'))
    reward = models.ForeignKey('Reward',blank=True,null=True,
        on_delete=models.SET_NULL)

    objects = PledgeManager()

    def get_deductible_total(self):
        return (self.amount - self.not_taxable) 

    @property
    def deductible_total(self):
        return self.get_deductible_total()


class Reward(models.Model):
    project = models.ForeignKey('Project')
    title = models.CharField(max_length=255)
    pledge_level = models.DecimalField(decimal_places=2, max_digits=10)
    deductible = models.DecimalField(decimal_places=2, max_digits=10)
    description = models.TextField(blank=True)

    def get_not_taxable(self):
        return (self.pledge_level - self.deductible)

    @property
    def not_taxable(self):
        return self.get_not_taxable()

因为我正在编辑项目应用程序中的models.py文件，所以我在项目上进行了迁移。也许支付应用还需要由于项目的变化而在其上运行迁移？

非常感谢您的帮助！

Answer 1

更改方法如下：

def get_deductible_total(self):
    return (self.amount - self.reward.not_taxable)

BTW通常在分离属性和方法方面没有任何意义，你也可以在属性中进行计算。你可以拥有

@property
def deductible_total(self):
    return (self.amount - self.not_taxable)

但有些理由将它们分开：
1）属性不会引发错误，所以如果你在需要异常的其他地方调用它，那么将它们分开是有意义的。
2）如果由于某种原因你需要一个返回结果的方法（或一个函数，基本上是一个可调用的），那么你还需要将它们分开。可能不是这种情况，可以使用lambda来对抗仅供参考。

Django：AttributeError：“对象没有属性”

1 个答案: