形成标准数据与查看数据 - 有什么区别？

Question

文件说:

In any form, the three different types of data are:

    Model data - This is the data in the format used in your application (e.g. an Issue object). If you call Form::getData() or Form::setData(), you're dealing with the "model" data.
    Norm Data - This is a normalized version of your data and is commonly the same as your "model" data (though not in our example). It's not commonly used directly.
    View Data - This is the format that's used to fill in the form fields themselves. It's also the format in which the user will submit the data. When you call Form::submit($data), the $data is in the "view" data format.

但我不明白规范数据和视图数据之间的区别.规范数据的用例是什么？文档中的下一段"那么为什么要使用模型变换器？" 对我没有任何意义.

Answer 1

我发现的最佳解释是在Symfony的Form类描述中:

<?php

...

namespace Symfony\Component\Form;

use ...

/**
 * Form represents a form.
 *
 * To implement your own form fields, you need to have a thorough understanding
 * of the data flow within a form. A form stores its data in three different
 * representations:
 *
 *   (1) the "model" format required by the form's object
 *   (2) the "normalized" format for internal processing
 *   (3) the "view" format used for display
 *
 * A date field, for example, may store a date as "Y-m-d" string (1) in the
 * object. To facilitate processing in the field, this value is normalized
 * to a DateTime object (2). In the HTML representation of your form, a
 * localized string (3) is presented to and modified by the user.
 *
 * In most cases, format (1) and format (2) will be the same. For example,
 * a checkbox field uses a Boolean value for both internal processing and
 * storage in the object. In these cases you simply need to set a value
 * transformer to convert between formats (2) and (3). You can do this by
 * calling addViewTransformer().
 *
 * In some cases though it makes sense to make format (1) configurable. To
 * demonstrate this, let's extend our above date field to store the value
 * either as "Y-m-d" string or as timestamp. Internally we still want to
 * use a DateTime object for processing. To convert the data from string/integer
 * to DateTime you can set a normalization transformer by calling
 * addNormTransformer(). The normalized data is then converted to the displayed
 * data as described before.
 *
 * The conversions (1) -> (2) -> (3) use the transform methods of the transformers.
 * The conversions (3) -> (2) -> (1) use the reverseTransform methods of the transformers.
 *
 * @author Fabien Potencier <fabien@symfony.com>
 * @author Bernhard Schussek <bschussek@gmail.com>
 */
class Form implements \IteratorAggregate, FormInterface
{
    ...
}

编辑:这是来自Sf form component(co)作者的视频,他解释了数据格式并给出了标准化格式使用的示例 - > https://youtu.be/Q80b9XeLUEA?t=7m6s

所以,基本上,每个表单都有三种不同格式的数据.前两个是:模型数据 - 您在域模型中使用的数据,以及视图数据 - 您通常以HTML格式输出的数据,或者在提交之前输入表单字段.

两个简单的例子是TextType和NumberType.在TextType中,模型数据是字符串,视图数据是字符串.

在NumberType中,模型数据是浮点数 - 在您的应用程序中,您正在处理浮点类型,而视图数据是本地化字符串.

但是,另一方面,如果我们看一下DateType,事情有点复杂,因为模型数据可能是字符串('YYYY-MM-DD'),整数(unix时间戳),数组或DateTime对象.视图数据可以是本地化字符串或数组.

例如,如果要编写事件侦听器,则无法确定将获得哪种数据格式:

class MyDateType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add...
            ->addEventListener(
                FormEvents::FormEvents::SUBMIT,
                array($this, 'onSubmit')
            )
        ;
    }

    public function onSubmit(FormEvent $event)
    {
        // BUT WHAT FORMAT DO I GET???
        $data = $event->getForm()->getData();
    }
}

幸运的是,Sf表格有第三种数据格式 - 规范化格式.这种格式是静态的 - 你总是知道你会得到什么,它总是相同的数据类型!

 public function onSubmit(FormEvent $event)
 {
     // $data will be DateTime object!
     $data = $event->getForm()->getNormData();
 }