Angular 2 Dynamic Forms:如何创建依赖下拉列表 [英] Angular 2 Dynamic Forms: How to create dependent dropdown

问题描述

我通过参考Angular 2 Dynamic Forms

一切正常.但我面临的问题是创建依赖下拉列表.例如:我想创建一个表单，用户可以在其中使用 Country、City、State 下拉菜单选择地址.

new DropdownField({键:'国家'，标签:'国家'，选项: [{键:'美国'，值:'美国'}，{键:'英国'，价值:'英国'}],订单:4}),新的下拉字段({键:'状态'，标签:'状态'，选项: [{key: 'taxas', value: 'taxas'},{键:'底特律'，值:'底特律'}],订单:5}),新的下拉字段({键:'城市'，标签:'城市',选项: [{键:'休斯顿'，值:'休斯顿'}，{键:'奥斯汀'，值:'奥斯汀'}],订单:5})

以下是模板.

<label [attr.for]="field.key" class="control-label">{{field.label}}</label><div [ngSwitch]="field.controlType"><input *ngSwitchCase="'文本框'"formControlName="{{field.key}}"[id]="field.key"[type]="field.type"类=形式控制"[占位符]="field.placeholder"[只读]="field.readonly"><select [id]="field.key" *ngSwitchCase="'dropdown'" formControlName="{{field.key}}" class="form-control"><option style="display:none" value="">选择一个选项</option><option *ngFor="let opt of field.options" [value]="opt.key">{{opt.value}}</option></选择>
<div style="颜色:红色;"*ngIf="!isValid">({{field.label}} 为必填项)

我想要的是当用户选择 Country 时，State 列表应该被填充，当用户选择 State 时， 列表City 应该被填充，但都使用动态表单.

解决方案

这是一个 Plunkr，它演示了依赖下拉列表:https://plnkr.co/edit/b5FKSp06XMfQul5pYQti?p=preview

它有一个用于选择产品类型(小型或大型)的第一个下拉列表，它更新第二个下拉列表，仅显示小型或大型产品.您可以轻松地将此示例转换为国家/州/城市的相关下拉列表.

Plunkr 展示了两种生成相关下拉列表值的技术:

• 重新计算第一个下拉列表发出的每个 change 事件 的值.
• 将自定义管道应用于相关下拉列表的值，以便它们自动绑定到 &按第一个下拉列表的值过滤.

I am creating dynamic form by referring to Angular 2 Dynamic Forms

Everything works good. but the problem I am facing is creating dependent drop-down. eg: I want to create form where user can select there address using Country, City, State drop-down.

new DropdownField({
  key: 'country',
  label: 'Country',
  options: [
    {key: 'usa',  value: 'USA'},
    {key: 'uk',  value: 'UK'}
  ],
  order: 4
}),

new DropdownField({
  key: 'state',
  label: 'State',
  options: [
    {key: 'taxas',  value: 'taxas'},
    {key: 'detroit',  value: 'detroit'}
  ],
  order: 5
}),

new DropdownField({
  key: 'city',
  label: 'City',
  options: [
    {key: 'houston',  value: 'Houston'},
    {key: 'austin',  value: 'Austin'}
  ],
  order: 5
})

Edit: Following is the template.

<div class="form-group" [formGroup]="form">
  <label [attr.for]="field.key" class="control-label">{{field.label}}</label>
  <div [ngSwitch]="field.controlType">
    <input *ngSwitchCase="'textbox'"
      formControlName="{{field.key}}"
      [id]="field.key"
      [type]="field.type"
      class="form-control"
      [placeholder]="field.placeholder"
      [readonly]="field.readonly"
    >
    <select [id]="field.key" *ngSwitchCase="'dropdown'" formControlName="{{field.key}}" class="form-control">
      <option style="display:none" value="">Choose an option</option>
      <option *ngFor="let opt of field.options" [value]="opt.key">{{opt.value}}</option>
    </select>
  </div>
  <div style="color: red;" *ngIf="!isValid">({{field.label}} is required)</div>
</div>

What I want is when user select Country, list of State should get populated and when user select State, list of City should get populated but all using Dynamic Forms.

解决方案

Here's a Plunkr which demonstrates dependent drop-downs: https://plnkr.co/edit/b5FKSp06XMfQul5pYQti?p=preview

It has a first drop-down list to select a product type (small or large) which updates a second drop-down list showing only the small or the large products. You could easily translate this example to dependent drop-downs for country/state/city.

The Plunkr shows two techniques to generate the values for the dependent drop-down:

• Recalculating the values on every change event emitted by the first drop-down.
• Applying a custom pipe to the values of the dependent drop-down so that they are automatically bound to & filtered by the value of the first drop-down.

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