Jinja2如果忽略布尔值 [英] Jinja2 If ignores boolean value

问题描述

我有一个Jinja2模板，其中解析为布尔假的变量在 {％if％} 语句中被忽略.

I have a Jinja2 template where a variable that resolves as a boolean False is being ignored in an {% if %} statement.

模板的相关块看起来像

{% if user.can_manage_techniques %}j
{% block submenu_items %}
<li class="pure-menu-item"><a href={{ url_for('new_technique') }} class="pure-menu-link">New Technique</a></li>
{% endblock %}
{% endif %}

用户在渲染模板中设置为

The user is set in render template as

    return render_template('technique_list.j2',
                            techniques=Technique.find_all(),
                            **state())

状态是返回dict [string，object]的函数.

with the state being a function that returns a dict[string, object].

传递给它的用户在对象的 __ init __ 中设置为变量-因此:

The user that is passed to it is set in the __init__ of the object as a variable - so:

    def __init__(self):
        self.can_manage_techniques = False

即使 can_manage_techniques 为false，列表项仍会呈现.如何使 {％if％} 意识到它是错误的，然后转到 {％endif％} ?

Even when the can_manage_techniques is false, the list item still renders. How do I make the {% if %} realise that it is false and go to the {% endif %}?

我也尝试过 == true 和 sameas true

推荐答案

我无法使用以下最少的应用程序在本地重现您的问题:

I can't reproduce your problem on local with minimal app below:

from flask import Flask, render_template_string
app = Flask(__name__)

@app.route('/')
def hello():
    return render_template_string('''
        {{ can }}
        {% if can %}
            {% block submenu_items %}
                <li class="pure-menu-item">New Technique</li>
            {% endblock %}
        {% endif %}
        ''', can=False)

IMO，用法是正确的，因此您可能需要检查更多相关代码.

IMO, the usage is correct, so you may need to check more related code.

在GitHub上检查代码后，我发现了为什么会发生这种情况.此问题是由模板继承行为引起的:在子模板中，块外的内容将被跳过.

I found why this happened after checking your code on GitHub. This issue caused by the template inheritance behavior: In child template, contents outside the block will be skipped.

由于模板是子模板，因此需要将if语句放入块中.

Since your template is child template, so you need to put the if statements into the block.

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