无法使模型 @property def-as-field 与 wagtail 2.0 一起使用 [英] Cannot make a model @property def-as-field work with wagtail 2.0

问题描述

我将 Wagtail 2.0 与具有以下代码的自定义块一起使用:

I'm using Wagtail 2.0 with a custom Block that has the following code:

class LinkButtonBlock(blocks.StructBlock):
    label = blocks.CharBlock()
    URL = blocks.CharBlock()
    styling = blocks.ChoiceBlock(
        choices=[
            ('btn-primary', 'Primary button'),
            ('btn-secondary', 'Secondary button'),
            ('btn-success', 'Success button'),
            ('btn-info', 'Info button'),
            ('btn-warning', 'Warning button'),
            ('btn-error', 'Error button'),
        ],
        default='btn-info',
    )
    outline = blocks.BooleanBlock(
        default=False
    )

    @property
    def css(self):
        btn_class = self.styling
        if self.outline is True:
            btn_class = btn_class.replace('btn-', 'btn-outline-')
            return btn_class

    class Meta:
        icon = 'link'
         template = 'testapp/blocks/link_button_block.html'

如果我尝试访问这个 css 属性"在我的模板中，似乎什么也没发生.将 print(self) 作为第一行放在 css def 中也不会在控制台上显示任何内容，表明该函数甚至从未被调用.

If I then try to access this css "property" in my template, nothing seems to happen. Putting a print(self) as first line inside the css def also shows nothing on the console suggesting the function never even gets called.

使用以下模板:

{% load wagtailcore_tags %}

<a class="btn {{ block.value.css }}" href="{{ block.value.URL }}">{{ block.value.label }}</a>

简单的收益:

<a class="btn " href="actual.url.from.instance">actual.label.from.instance</a>

此外，block.value.styling 和 block.value.outline 自己的工作也很好，所以......我在这里做错了什么?

Also, block.value.styling and block.value.outline on their own work just fine, so... what am I doing wrong here?

推荐答案

让您感到困惑的是，您在遍历 StreamField 时获得的值对象不是 StructBlock 的实例.StructBlock 和 CharBlock 等块对象充当不同数据表示之间的转换器；他们不会自己保留数据.在这方面，它们的工作方式很像 Django 的表单字段对象；例如，Django 的 forms.CharField 和 Wagtail 的 CharBlock 都定义了如何将字符串呈现为表单字段，以及如何从表单提交中检索字符串.

The thing that's tripping you up is that the value objects you get when iterating over a StreamField are not instances of StructBlock. Block objects such as StructBlock and CharBlock act as converters between different data representations; they don't hold on to the data themselves. In this respect, they work a lot like Django's form field objects; for example, Django's forms.CharField and Wagtail's CharBlock both define how to render a string as a form field, and how to retrieve a string from a form submission.

请注意，CharBlock 适用于字符串对象 - 而不是 CharBlock 的实例.同样，从 StructBlock 返回的值不是 StructBlock 的实例 - 它们是 StructValue 类型的类似 dict 的对象，并且 this 是实现 css 属性所需的子类.在文档中有一个这样做的例子:http://docs.wagtail.io/en/v2.0/topics/streamfield.html#custom-value-class-for-structblock.应用于您的代码，这将变成:

Note that CharBlock works with string objects - not instances of CharBlock. Likewise, the values returned from StructBlock are not instances of StructBlock - they are a dict-like object of type StructValue, and this is what you need to subclass to implement your css property. There's an example of doing this in the docs: http://docs.wagtail.io/en/v2.0/topics/streamfield.html#custom-value-class-for-structblock. Applied to your code, this would become:

class LinkButtonValue(blocks.StructValue):
    @property
    def css(self):
        # Note that StructValue is a dict-like object, so `styling` and `outline`
        # need to be accessed as dictionary keys
        btn_class = self['styling']
        if self['outline'] is True:
            btn_class = btn_class.replace('btn-', 'btn-outline-')
        return btn_class

class LinkButtonBlock(blocks.StructBlock):
    label = blocks.CharBlock()
    URL = blocks.CharBlock()
    styling = blocks.ChoiceBlock(choices=[...])
    outline = blocks.BooleanBlock(default=False)

    class Meta:
        icon = 'link'
        template = 'testapp/blocks/link_button_block.html'
        value_class = LinkButtonValue

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