271 lines
11 KiB
Markdown
271 lines
11 KiB
Markdown
# Dynamic Forms
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# 动态表单
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{@a top}
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Building handcrafted forms can be costly and time-consuming,
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especially if you need a great number of them, they're similar to each other, and they change frequently
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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
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metadata that describes 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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This cookbook shows you how to use `formGroup` to dynamically
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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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The example in this cookbook is a dynamic form to build an
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online application experience for heroes seeking employment.
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The agency is constantly tinkering with the application process.
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You can create the forms on the fly *without changing the 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 toc}
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See the <live-example name="dynamic-form"></live-example>.
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参见<live-example name="dynamic-form"></live-example>。
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{@a bootstrap}
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## Bootstrap
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## 启动/引导 (bootstrap)
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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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This cookbook uses [reactive forms](guide/reactive-forms).
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这个烹饪书使用[响应式表单](guide/reactive-forms)。
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Reactive forms belongs to a different `NgModule` called `ReactiveFormsModule`,
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so in order to access any reactive forms directives, you have to import
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`ReactiveFormsModule` from the `@angular/forms` library.
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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，我们得从 `@angular/forms` 库中引入 `ReactiveFormsModule` 模块。
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Bootstrap the `AppModule` in `main.ts`.
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我们在 `main.ts` 中启动 `AppModule`。
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<code-tabs>
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<code-pane title="app.module.ts" path="dynamic-form/src/app/app.module.ts">
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</code-pane>
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<code-pane title="main.ts" path="dynamic-form/src/main.ts">
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</code-pane>
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</code-tabs>
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{@a object-model}
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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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The following `QuestionBase` is a 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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<code-example path="dynamic-form/src/app/question-base.ts" title="src/app/question-base.ts">
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</code-example>
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From this base you can derive two new classes in `TextboxQuestion` and `DropdownQuestion`
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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
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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 such as text, email, and url
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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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<code-example path="dynamic-form/src/app/question-textbox.ts" title="src/app/question-textbox.ts" linenums="false">
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</code-example>
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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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<code-example path="dynamic-form/src/app/question-dropdown.ts" title="src/app/question-dropdown.ts" linenums="false">
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</code-example>
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Next is `QuestionControlService`, a simple service for transforming the questions to a `FormGroup`.
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In a nutshell, the form group consumes the metadata from the question model and
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allows you 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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<code-example path="dynamic-form/src/app/question-control.service.ts" title="src/app/question-control.service.ts" linenums="false">
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</code-example>
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{@a form-component}
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## Question form components
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## 问卷表单组件
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Now that you have defined the complete model you are ready
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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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`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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<code-tabs>
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<code-pane title="dynamic-form.component.html" path="dynamic-form/src/app/dynamic-form.component.html">
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</code-pane>
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<code-pane title="dynamic-form.component.ts" path="dynamic-form/src/app/dynamic-form.component.ts">
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</code-pane>
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</code-tabs>
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It presents a list of questions, each bound to a `<app-question>` component element.
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The `<app-question>` tag matches the `DynamicFormQuestionComponent`,
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the component responsible for rendering the details of each _individual_
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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 `<app-question>` 组件元素。
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`<app-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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<code-tabs>
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<code-pane title="dynamic-form-question.component.html" path="dynamic-form/src/app/dynamic-form-question.component.html">
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</code-pane>
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<code-pane title="dynamic-form-question.component.ts" path="dynamic-form/src/app/dynamic-form-question.component.ts">
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</code-pane>
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</code-tabs>
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Notice this component can present any type of question in your model.
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You only have two types of questions at this point but you 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 you'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
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`ReactiveFormsModule`. The templates can access these directives
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directly since you 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 questionnaire-data}
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## Questionnaire data
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## 问卷数据
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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 you've defined for the job application is returned from the `QuestionService`.
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In a real app you'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 you control the hero job application questions
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entirely through the objects returned from `QuestionService`.
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Questionnaire maintenance is a simple matter of adding, updating,
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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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<code-example path="dynamic-form/src/app/question.service.ts" title="src/app/question.service.ts">
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</code-example>
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Finally, 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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<code-example path="dynamic-form/src/app/app.component.ts" title="app.component.ts">
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</code-example>
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{@a dynamic-template}
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## Dynamic Template
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## 动态模板
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Although in this example you're modelling a job application for heroes, there are
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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 you to repurpose the components for any type of survey
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as long as it's compatible with the *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, you 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, you 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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The final form looks like this:
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完整的表单是这样的：
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<figure>
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<img src="generated/images/guide/dynamic-form/dynamic-form.png" alt="Dynamic-Form">
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</figure>
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[Back to top](guide/dynamic-form#top)
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[回到顶部](guide/dynamic-form#top)
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