django - Django:无法在模板内进行计算
问题描述
我创建了一个电子商务 Django 应用程序,在这个应用程序的后台,我有一个页面应该显示一些统计信息。我试图展示收益或损失。对于成本,我在模型中创建了一个@property,如下所示:
class Statistics(models.Model):
"""
The Statistics model represents the statistics that can be calculated
"""
costs_infra = models.FloatField(verbose_name="Costs Infrastructure")
costs_salary = models.FloatField(verbose_name="Costs Salary")
class Meta:
verbose_name_plural = "Statistics"
def __str__(self):
"""Unicode representation of Statistics"""
return " Infra costs: {}, Salary costs: {}".format(
self.costs_infra,
self.costs_salary
)
@property
def calculate_costs(self):
return self.costs_infra + self.costs_salary
对于总收入,我在一个视图中计算如下:
@group_required('Administrator', 'Manager')
def stats_home(request):
total_users = User.objects.all().count()
costs = Statistics.objects.all()
subscriptions_1month = Subscription.objects.get(plan_name='1 Month')
subscriptions_1year = Subscription.objects.get(plan_name='1 Year')
subscriptions_3year = Subscription.objects.get(plan_name='3 Years')
user_subscriptions_1month = UserSubscription.objects.filter(subscription=subscriptions_1month).annotate(Count('user', distinct=True)).count()
user_subscriptions_1year = UserSubscription.objects.filter(subscription=subscriptions_1year).annotate(Count('user', distinct=True)).count()
user_subscriptions_3years = UserSubscription.objects.filter(subscription=subscriptions_3year).annotate(Count('user', distinct=True)).count()
income_per_subscription_1month = Subscription.objects.get(plan_name='1 Month').price * UserSubscription.objects.filter(subscription=subscriptions_1month).count()
income_per_subscription_1year = Subscription.objects.get(plan_name='1 Year').price * UserSubscription.objects.filter(subscription=subscriptions_1year).count()
income_per_subscription_3years = Subscription.objects.get(plan_name='3 Years').price * UserSubscription.objects.filter(subscription=subscriptions_3year).count()
total_income = income_per_subscription_1month + income_per_subscription_1year + income_per_subscription_3years
return render (request, "stats_home.html", locals())
最后,我正在尝试进行简单的计算(总收入 - 总成本),但据我所知,我无法在模板中执行此操作,并且我的研究引导了我。
{% extends 'base.html' %}
{% load crispy_forms_tags %}
{% load has_group %}
{% block title %} Statistics Home {% endblock %}
{% block content %}
<div class="card border-dark mb-4" id="profil">
<h5 class="card-header bg-dark text-white">Total number of users subscribed to the site:</h5>
<div class="card-body">
{{total_users}}
</div>
</div>
<div class="card border-dark mb-4" id="profil">
<h5 class="card-header bg-dark text-white">Total number of users per subscription type:</h5>
<div class="card-body">
<br>1 Month: {{user_subscriptions_1month}}
<br>1 Year: {{user_subscriptions_1year}}
<br>3 Years: {{user_subscriptions_3years}}
</div>
</div>
<div class="card border-dark mb-4" id="profil">
<h5 class="card-header bg-dark text-white">Costs:</h5>
<div class="card-body">
{% for cost in costs %}
<p>Infrastructure Costs: {{cost.costs_infra}}</p>
<p>Salary Costs: {{cost.costs_salary}}</p>
<p>Total Costs: {{cost.calculate_costs}}</p>
{% endfor %}
</div>
</div>
<div class="card border-dark mb-4" id="profil">
<h5 class="card-header bg-dark text-white"> Total Income: </h5>
<div class="card-body">
{{total_income}}
</div>
</div>
<div class="card border-dark mb-4" id="profil">
<h5 class="card-header bg-dark text-white"> Benefits/Loss: </h5>
<div class="card-body">
Benefits/Loss: {{total_income - cost.calculate_costs}}
</div>
</div>
通过执行 {{total_income - cost.calculate_costs}} 我得到一个错误
无法解析剩余部分:来自“total_income - cost.calculate_costs”的“-cost.calculate_costs”
问题是我可以用 {{cost.calculate_costs}} 获得总成本,用 {{total_income}} 获得总收入,但不知何故我无法在模板中进行简单的减法。
实现这一目标的最佳方法是什么?
解决方案
您可以做的最好的事情是,不要在模板中进行计算,而是在视图中进行,因为建议不要在模板中这样做,因为它会降低网站的性能,而是这样做:
视图.py
variable = total_income - total_costs
context = {"variable":variable}
return render(request, "stats_home.html", locals(), context)
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