262 lines
12 KiB
Plaintext
262 lines
12 KiB
Plaintext
include ../_util-fns
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:marked
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We can't always justify the cost and time to build handcrafted forms, especially if we'll need a great number of them, they're similar to each other, and they change frequently to meet rapidly changing business and regulatory requirements.
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有时候手动编写和维护表单所需工作量和时间会过大。特别是在需要编写大量表单时。表单都很相似，而且随着业务和监管需求的迅速变化，表单也要随之变化，这样维护的成本过高。
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It may be more economical to create the forms dynamically, based on metadata that describe the business object model.
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基于业务对象模型的元数据，动态创建表单可能会更划算。
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In this cookbook we show how to use `formGroup` to dynamically render a simple form with different control types and validation.
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It's a primitive start.
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It might evolve to support a much richer variety of questions, more graceful rendering, and superior user experience.
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All such greatness has humble beginnings.
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在此烹饪宝典中，我们会展示如何利用`formGroup`来动态渲染一个简单的表单，包括各种控件类型和验证规则。
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这个起点很简陋，但可以在这个基础上添加丰富多彩的问卷问题、更优美的渲染以及更卓越的用户体验。
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In our example we use a dynamic form to build an online application experience for heroes seeking employment.
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The agency is constantly tinkering with the application process.
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We can create the forms on the fly *without changing our application code*.
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在本例中，我们使用动态表单，为正在找工作的英雄们创建一个在线申请表。英雄管理局会不断修改申请流程，我们要在*不修改应用代码*的情况下，动态创建这些表单。
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<a id="toc"></a>
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:marked
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## Table of contents
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## 目录
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[Bootstrap](#bootstrap)
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[程序启动](#bootstrap)
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[Question Model](#object-model)
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[问卷问题模型](#object-model)
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[Form Component](#form-component)
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[表单组件](#form-component)
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[Questionnaire Metadata](#questionnaire-metadata)
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[问卷元数据](#questionnaire-metadata)
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[Dynamic Template](#dynamic-template)
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[动态模板](#dynamic-template)
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:marked
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**See the <live-example name="cb-dynamic-form"></live-example>**.
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**参见<live-example name="cb-dynamic-form">在线例子</live-example>**。
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.l-main-section
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<a id="bootstrap"></a>
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:marked
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## Bootstrap
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## 程序启动
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We start by creating an `NgModule` called `AppModule`.
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让我们从创建一个名叫`AppModule`的`NgModule`开始。
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In our example we will be using Reactive Forms.
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在本例子中，我们将使用响应式表单（Reactive Forms）。
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Reactive Forms belongs to a different `NgModule` called `ReactiveFormsModule`, so in order to access any Reactive Forms directives, we have to import `ReactiveFormsModule` from `AppModule`.
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响应式表单属于另外一个叫做`ReactiveFormsModule`的`NgModule`，所以，为了使用响应式表单类的指令，我们得往`AppModule`中引入`ReactiveFormsModule`模块。
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We bootstrap our `AppModule` in main.ts.
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我们在main.ts中启动`AppModule`。
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+makeTabs(
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`cb-dynamic-form/ts/app/app.module.ts,
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cb-dynamic-form/ts/app/main.ts`,
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null,
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`app.module.ts,
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main.ts`
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)
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.l-main-section
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<a id="object-model"></a>
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:marked
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## Question Model
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## 问卷问题模型
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The next step is to define an object model that can describe all scenarios needed by the form functionality.
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The hero application process involves a form with a lot of questions.
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The "question" is the most fundamental object in the model.
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第一步是定义一个对象模型，用来描述所有表单功能需要的场景。英雄的申请流程涉及到一个包含很多问卷问题的表单。问卷问题是最基础的对象模型。
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We have created `QuestionBase` as the most fundamental question class.
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下面是我们建立的最基础的问卷问题基类，名叫`QuestionBase`。
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+makeExample('cb-dynamic-form/ts/app/question-base.ts','','app/question-base.ts')
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:marked
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From this base we derived two new classes in `TextboxQuestion` and `DropdownQuestion` that represent Textbox and Dropdown questions.
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The idea is that the form will be bound to specific question types and render the appropriate controls dynamically.
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在这个基础上，我们派生出两个新类`TextboxQuestion` 和 `DropdownQuestion`，分别代表文本框和下拉框。这么做的初衷是，表单能动态绑定到特定的问卷问题类型，并动态渲染出合适的控件。
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`TextboxQuestion` supports multiple html5 types like text, email, url etc via the `type` property.
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`TextboxQuestion`可以通过`type`属性来支持多种HTML5元素类型，比如文本、邮件、网址等。
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+makeExample('cb-dynamic-form/ts/app/question-textbox.ts',null,'app/question-textbox.ts')(format='.')
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:marked
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`DropdownQuestion` presents a list of choices in a select box.
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`DropdownQuestion`表示一个带可选项列表的选择框。
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+makeExample('cb-dynamic-form/ts/app/question-dropdown.ts',null,'app/question-dropdown.ts')(format='.')
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:marked
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Next we have defined `QuestionControlService`, a simple service for transforming our questions to a `FormGroup`.
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In a nutshell, the form group consumes the metadata from the question model and allows us to specify default values and validation rules.
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接下来，我们定义了`QuestionControlService`，一个可以把问卷问题转换为`FormGroup`的服务。
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简而言之，这个`FormGroup`使用问卷模型的元数据，并允许我们设置默认值和验证规则。
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+makeExample('cb-dynamic-form/ts/app/question-control.service.ts',null,'app/question-control.service.ts')(format='.')
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<a id="form-component"></a>
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:marked
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## Question form components
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## 问卷表单组件
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Now that we have defined the complete model we are ready to create components to represent the dynamic form.
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现在我们已经有一个定义好的完整模型了，接着就可以开始创建一个展现动态表单的组件。
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:marked
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`DynamicFormComponent` is the entry point and the main container for the form.
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`DynamicFormComponent`是表单的主要容器和入口点。
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+makeTabs(
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`cb-dynamic-form/ts/app/dynamic-form.component.html,
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cb-dynamic-form/ts/app/dynamic-form.component.ts`,
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null,
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`dynamic-form.component.html,
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dynamic-form.component.ts`
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)
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:marked
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It presents a list of questions, each question bound to a `<df-question>` component element.
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The `<df-question>` tag matches the `DynamicFormQuestionComponent`,
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the component responsible for rendering the details of each _individual_ question based on values in the data-bound question object.
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它代表了问卷问题列表，每个问题都被绑定到一个`<df-question>`组件元素。
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`<df-question>`标签匹配到的是组件`DynamicFormQuestionComponent`，该组件的职责是根据各个问卷问题对象的值来动态渲染表单控件。
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+makeTabs(
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`cb-dynamic-form/ts/app/dynamic-form-question.component.html,
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cb-dynamic-form/ts/app/dynamic-form-question.component.ts`,
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null,
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`dynamic-form-question.component.html,
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dynamic-form-question.component.ts`
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)
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:marked
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Notice this component can present any type of question in our model.
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We only have two types of questions at this point but we can imagine many more.
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The `ngSwitch` determines which type of question to display.
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请注意，这个组件能代表模型里的任何问题类型。目前，还只有两种问题类型，但可以添加更多类型。可以用`ngSwitch`决定显示哪种类型的问题。
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In both components we're relying on Angular's **formGroup** to connect the template HTML to the
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underlying control objects, populated from the question model with display and validation rules.
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在这两个组件中，我们依赖Angular的**formGroup**来把模板HTML和底层控件对象连接起来，该对象从问卷问题模型里获取渲染和验证规则。
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`formControlName` and `formGroup` are directives defined in `ReactiveFormsModule`. Our templates can can access these directives directly since we imported `ReactiveFormsModule` from `AppModule`.
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`formControlName`和`formGroup`是在`ReactiveFormsModule`中定义的指令。我们之所以能在模板中使用它们，是因为我们往`AppModule`中导入了`ReactiveFormsModule`。
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<a id="questionnaire-metadata"></a>
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:marked
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## Questionnaire data
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## 问卷数据
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:marked
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`DynamicFormComponent` expects the list of questions in the form of an array bound to `@Input() questions`.
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`DynamicForm`期望得到一个问题列表，该列表被绑定到`@Input() questions`属性。
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The set of questions we have defined for the job application is returned from the `QuestionService`.
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In a real app we'd retrieve these questions from storage.
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`QuestionService`会返回为工作申请表定义的那组问题列表。在真实的应用程序环境中，我们会从数据库里获得这些问题列表。
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The key point is that we control the hero job application questions entirely through the objects returned from `QuestionService`.
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Questionnaire maintenance is a simple matter of adding, updating, and removing objects from the `questions` array.
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关键是，我们完全根据`QuestionService`返回的对象来控制英雄的工作申请表。
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要维护这份问卷，只要非常简单的添加、更新和删除`questions`数组中的对象就可以了。
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+makeExample('cb-dynamic-form/ts/app/question.service.ts','','app/question.service.ts')
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:marked
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Finally, we display an instance of the form in the `AppComponent` shell.
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最后，在`AppComponent`里显示出表单。
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+makeExample('cb-dynamic-form/ts/app/app.component.ts','','app.component.ts')
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<a id="dynamic-template"></a>
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:marked
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## Dynamic Template
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## 动态模板
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Although in this example we're modelling a job application for heroes, there are no references to any specific hero question
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outside the objects returned by `QuestionService`.
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在这个例子中，虽然我们是在为英雄的工作申请表建模，但是除了`QuestionService`返回的那些对象外，没有其它任何地方是与英雄有关的。
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This is very important since it allows us to repurpose the components for any type of survey
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as long as it's compatible with our *question* object model.
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The key is the dynamic data binding of metadata used to render the form
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without making any hardcoded assumptions about specific questions.
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In addition to control metadata, we are also adding validation dynamically.
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这点非常重要，因为只要与*问卷*对象模型兼容，就可以在任何类型的调查问卷中复用这些组件。
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这里的关键是用到元数据的动态数据绑定来渲染表单，对问卷问题没有任何硬性的假设。除控件的元数据外，还可以动态添加验证规则。
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The *Save* button is disabled until the form is in a valid state.
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When the form is valid, we can click *Save* and the app renders the current form values as JSON.
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This proves that any user input is bound back to the data model.
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Saving and retrieving the data is an exercise for another time.
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表单验证通过之前，*保存*按钮是禁用的。验证通过后，就可以点击*保存*按钮，程序会把当前值渲染成JSON显示出来。
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这表明任何用户输入都被传到了数据模型里。至于如何储存和提取数据则是另一话题了。
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:marked
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The final form looks like this:
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完整的表单看起来是这样的：
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figure.image-display
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img(src="/resources/images/cookbooks/dynamic-form/dynamic-form.png" alt="Dynamic-Form")
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:marked
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[Back to top](#top)
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[回到顶部](#top)
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