如何在 WTForms 中渲染可变长度的字段列表?

Question

我正在尝试制作一个表单来填充日历。日历可以是五到七天，我想将天数作为参数传递给表单。我的表单定义如下：

class LoadForecastForm(Form):
def __init__(self, n_days, *args, **kwargs):
self.n_days = n_days
super(LoadForecastForm, self).__init__(*args, **kwargs)
self.day_values = FieldList(SelectField('Day Values', coerce=str, choices=[('low', 'Low'), ('medium', 'Medium'), ('high', 'High'), ('holiday', 'Holiday')]), min_entries=n_days, max_entries=n_days)
self.send = SubmitField('Send Calendar')

它的呈现方式如下：

<form role="form" action="" method="POST">
{{ form.hidden_tag() }}
<div class="form-group row">
{% for field in form.day_values %}
<div class="col-sm-2">
<div class="form-group{% if field.errors %} error {% endif %}">
{% if label %}
{{ field.label }}
{% endif %}
{{ field(**kwargs) }}
{% for error in field.errors %}
<span class="help-inline">[{{error}}]</span><br>
{% endfor %}
</div>
</div>
{% endfor %}
</div>
{{ form.send }}

表单页面无法呈现;回溯以以下结尾：

File "project/populate_schedule.tpl.html", line 25, in block "page_content"
{% for field in day_values %}
TypeError: 'UnboundField' object is not iterable

n_days过去是硬编码的，字段被定义为没有__init__()函数的类变量，并且没有错误。如何以编程方式正确定义字段？我正在使用Python 2.7。

Answer 1

您需要将字段定义保留在类主体中，否则它们将不会随着类的构造而被拾取。 初始化表单实例时，您可以将最大/最小条目值应用于字段列表。

class F(Form):
day_values = FieldList(SelectField('Day Values',
coerce=str,
choices=[('low', 'Low'), ('medium', 'Medium'),
('high', 'High'), ('holiday', 'Holiday')]))
send = SubmitField('Send Calendar')
def __init__(self, *args, **kwargs):
ndays = kwargs.pop('n_days')
super(F, self).__init__(*args, **kwargs)
self.day_values.min_entries = n_days
self.day_values.max_entries = n_days

测试：

n_days = 4
f = F(n_days=n_days)
for x in range(n_days):
f.day_values.append_entry()
for field in f.day_values:
print field()
print

输出：

<select id="day_values-0" name="day_values-0"><option value="low">Low</option><option value="medium">Medium</option><option value="high">High</option><option value="holiday">Holiday</option></select>
<select id="day_values-1" name="day_values-1"><option value="low">Low</option><option value="medium">Medium</option><option value="high">High</option><option value="holiday">Holiday</option></select>
<select id="day_values-2" name="day_values-2"><option value="low">Low</option><option value="medium">Medium</option><option value="high">High</option><option value="holiday">Holiday</option></select>
<select id="day_values-3" name="day_values-3"><option value="low">Low</option><option value="medium">Medium</option><option value="high">High</option><option value="holiday">Holiday</option></select>