英文:
Showing property filter value in Django template
问题
I couldn't get the value of the LastActiveTrack in my template. Any ideas?
在我的模板中，我无法获取LastActiveTrack的值。有什么想法吗？
英文:
I have the follwoing models in my Django project:
class File(models.Model):client = models.ForeignKey(User, on_delete=models.PROTECT, related_name='client_files')title = models.CharField(max_length=250, blank=True, null=True)...
class FileTracking(models.Model):file = models.ForeignKey(File, related_name='file_tracking', on_delete=models.CASCADE)description = models.CharField(max_length=250, null=True, blank=True)title = models.CharField(max_length=250, blank=True, null=True)date = models.DateField(auto_now=False, auto_now_add=False)active = models.BooleanField(default=False)...
my view:
class FileCurrentView(ListView):model = Filetemplate_name = 'files_current.html'def get_context_data(self, **kwargs):context = super().get_context_data(**kwargs)if self.request.user.is_authenticated:user=self.request.usercurrent_files = files.filter(...)...context["user"] = usercontext["current_files"]= current_files...return context
In my template, I want to show the description or title of the last active record.
I tried to create a property in the FileTracking model:
@propertydef LastActiveTrack(self):result = self.objects.filter(active=1).order_by("-date")[0].titleresult_txt = str(result)if result:return result_txtreturn ''
in my template:
{% for file in current_files %}Title: {{file.title}}last Tracking: {{file.file_tracking.LastActiveTrack}}{% endif %}
but I couldn't get the value of the LastActiveTrack in my template. Any ideas?
答案1
得分: 0
在模板中这样做不太理想，因为你会为每个文件进行一次数据库调用，如果文件很多，这可能会导致不必要的开销。
更好的方法是更新你的初始调用，包括每个文件的文件跟踪信息，可以使用prefetch_related来实现，这应该限制为两次数据库调用。
current_files = files.filter(...).prefetch_related(Prefetch('file_tracking',queryset=FileTracking.objects.order_by("-date"),# 为了在模板中明确引用，可以在Prefetch中添加一个to_attr参数to_attr="filetrack_ordered"))
然后在你的模板中可以这样调用：
{% for file in current_files %}Title: {{file.title}}Last Tracking: {{file.filetrack_ordered.0.title}}{% endfor %}
注意：在你的问题中，似乎你正在寻找file_tracking.title，但在你提供的模型字段中并没有实际提到。我假设它在模型中的某个地方。
<details><summary>英文:</summary>Doing this in your template is less than ideal as you will make a database call for each file, which may get expensive in overhead if you have a lot of files.Better to update your initial call to include each file's filtracking via [prefetch_related][1], which should limit it to two DB callscurrent_files = files.filter(...).prefetch_related(Prefetch('file_tracking',queryset=FileTracking.objects.order_by("-date"),#to make it clear what we are referring to in our template#add a to_attr argument to Prefetchto_attr="filetrack_ordered"))then in your template you can call:{% for file in current_files %}Title: {{file.title}}last Tracking: {{file.filetrack_ordered.0.title}}{% endif %}NB: in your question you seem to be looking for file_tracking.title which isn't actually mentioned in the model fields you provide. I've assumed it's in there somewhere.[1]: https://docs.djangoproject.com/en/4.2/ref/models/querysets/#prefetch-related</details>
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