WTForms/Flask：动态 min_entries

Question

我希望动态使用 min_entries WTForms 参数，即不使用硬编码数字。

它在 form.py 中看起来像这样：

class TestSpecForm(FlaskForm): 
    student_number = IntegerField('Number of Students')


class StudentForm(FlaskForm):
    answer = StringField('')


class TestInputForm(FlaskForm):
    students = FieldList(FormField(StudentForm))  # I'd like to insert the dynamic min_entries here
    submit = SubmitField('Submit')

以及views.py中的类似内容：

def input(key_id):
    key = Testspecs.query.get_or_404(key_id) 
    student_number = key.student_number
    form = TestInputForm()
    form.students.min_entries = student_number
    if form.validate_on_submit():
        ...

但是，这不起作用，只会为 TestInputForm 呈现 NO FIELDS。如果我将“min_entries = 10”放入 TestInputForm 的学生变量中，一切都会按预期工作。但我无法动态完成它。

谁能帮帮我？根据我所有的 google/reddit/SO 搜索，这基本上是 WTForms 中大多数参数或验证器的动态设置方式。

谢谢

Answer 1

我刚刚发现了字段列表和表单字段，并在互联网上搜索了文档或示例，但几乎没有找到任何帮助。我想出了在渲染模板时获取动态条目数的好方法，所以我想我会在这里提交它以防它对任何人有帮助。请注意，这并不涉及使用按钮或类似的东西即时添加条目。

def input(key_id):
    key = Testspecs.query.get_or_404(key_id) 
    student_number = key.student_number
    form = TestInputForm()
    # if the form was submitted, then it will collect all the entries for us
    if form.validate_on_submit():
        # form has whatever entries were just submitted
        for entry in form.students.entries:
            ...
        return(redirect(...))
    # if we get here, either validation failed or we're just loading the page
    # we can use append_entry to add up to the total number we want, if necessary
    for i in range(len(form.students.entries), student_number):
        form.students.append_entry()
    return render_template("input.html", form=form)

Answer 2

无法动态覆盖FieldList 上的min_entries。

解决方法是子类化表单并将新的FieldList 绑定到所需的值。

所以你的代码必须看起来像这样：

def input(key_id):
    key = Testspecs.query.get_or_404(key_id) 
    student_number = key.student_number
    # Subclass form and bind new field
    class LocalForm(TestInputForm):pass
    LocalForm.students = FieldList(FormField(StudentForm), min_entries=student_number)
    # Use our new form
    form = LocalForm()
    if form.validate_on_submit():
        ...