Question

我需要在Django模板上显示消息。每个消息可以有0到许多评论。我需要显示每条消息的评论。但是，如果一条消息没有评论，则为“无”，我无法对其进行迭代。该问题发生在Django模板中。

#models.py
class User(models.Model):
    firstName = models.CharField(max_length = 255)
    lastName = models.CharField(max_length = 255)
    email = models.CharField(max_length = 255)
    birthDate = models.DateField()
    password = models.CharField(max_length = 255)
    createdAt = models.DateTimeField(auto_now_add = True)
    updatedAt = models.DateTimeField(auto_now = True)
    objects = UserManager()

class Message(models.Model):
    content = models.TextField()
    user = models.ForeignKey(User, related_name = "messages")
    createdAt = models.DateTimeField(auto_now_add = True)
    updatedAt = models.DateTimeField(auto_now = True)
    objects = UserManager()

class Comment(models.Model):
    content = models.TextField()
    message = models.ForeignKey(Message, related_name = "comments", default = [])
    createdAt = models.DateTimeField(auto_now_add = True)
    updatedAt = models.DateTimeField(auto_now = True)
    objects = UserManager()

#views.py
#Main wall page
#Renders wall.html
def wall(request):

    wallDict = {
        "message" : Message.objects.all()
    }

    return render(request, "loginRegApp/wall.html", wallDict)

#wall.html
<!DOCTYPE html>
<html lang="en">
    <head>
        <title></title>
        <meta charset="utf-8">
    </head>
    <body>
        <div class="container">
            <a href="/logout">Log out</a>
            <form action="message/create" method="post">
                {% csrf_token %}
                <h4>Post a message</h4>
                <textarea name="message"></textarea>
                <input type="submit" value="Post a message">
            </form>

            {% for message in messages %}
                <div>
                    <h6>{{message.user.firstName}} {{message.user.lastName}} - {{message.createdAt}}</h6>
                    <p>{{message.content}}</p>

                    {% if message.comments %}
                    {% for comment in message.comments %}
                        <h6>Comment:  {{message.user.firstName}} {{message.user.lastName}} - {{comment.createdAt}}</h6>
                        <p>{{comment.content</p>
                    {% endfor %}
                    {% endif %}

                    <form action="comment/{{message.id}}/create" method="post">
                        {% csrf_token %}
                        <textarea name="comment"></textarea>
                        <input type="submit" value="Post a comment">
                    </form>
                </div>
            {% endfor %}
        </div>
    </body>
</html>

我正在尝试显示所有注释，无论是0还是100。

Answer 1

您应该在模板中使用.all才能访问包含注释的QuerySet。无需使用{% if ... %}和{% endif %}：

{% for comment in message.comments.all %}
    <h6>Comment:  {{message.user.firstName}} {{message.user.lastName}} - {{comment.createdAt}}</h6>
    <p>{{comment.content</p>
{% endfor %}

在您看来，您可能希望在此处使用.prefetch_related(..) [Django-doc]以避免对每条消息进行额外查询以获取相关评论，例如：

def wall(request):
    wallDict = {
        'message' : Message.objects.prefetch_related(
            'comments', 'comments__user'
        ).all()
    }
    return render(request, 'loginRegApp/wall.html', wallDict)

仅在存在问题时显示评论

1 个答案: