如何使用Angular 2应用程序中的typescript显示基于其他下拉值的下拉值

Question

我正在开发angular 2应用程序,在我目前的项目中,我想要显示基于年份,品牌,型号的下拉值的功能.例如,如果我选择本田,那么在模型下拉列表中仅显示本田车型.

默认情况下,我将绑定年份,品牌和型号的完整数据.

这是我的观点.

VehicleComponent.html

  <div class="row form-group">
                                    <div class="col-md-3">
                                        <label  class="control-label">Year*</label><br />
                                        <select  friendly-name="Year" id="year" name="year" class="col-md-6 form-control"  ng-required="true" onchange='OnChange()' >
                                            <option>Select</option>

                                            <option *ngFor='let type of lookupdetailsvehicleyearinfo'>{{type.LookupValue}}</option>

                                        </select>
                                    </div>
                                    <div class="col-md-3">
                                        <label  class="control-label">Make*</label><br />
                                        <select friendly-name="Make" class="col-md-6 form-control" ng-required="true" >
                                            <option>Select</option>
                                            <option *ngFor='let type of lookupdetailsvehiclemakeinfo'>{{type.LookupValue}}</option>
                                            </select>
                                    </div>
                                    <div class="col-md-3">
                                        <label  class="control-label">Model*</label>
                                        <select  friendly-name="Model" class="col-md-6 form-control" ng-required="true" >
                                            <option>Select</option>
                                            <option *ngFor='let type of lookupdetailsvehiclemodelinfo'>{{type.LookupValue}}</option>
                                           </select>
                                    </div>                                      
                                </div>

我将从My Own API获得上述数据.

您能告诉我如何在angular 2应用程序中编写typescript代码以获得上述功能.

Answer 1

您唯一需要做的就是跟踪changeselect-input 的事件并更改另一个select-input的来源.Angular2将完成剩下的工作.

使用选中的value:

@Component({
  selector: 'my-app',
  template: `
    <div>
      <h2>Hello {{name}}</h2>

      <select (change)="firstDropDownChanged($event.target.value)" >
        <option>Select</option>
        <option *ngFor='let v of _values1'>{{ v }}</option>
      </select>

      <select >
        <option>Select</option>
        <option *ngFor='let v of _values2'>{{ v }}</option>
      </select>
    </div>
  `,
})
export class App {
  name:string;

  private _values1 = ["1", "2", "3"];
  private _values2 = [];

  constructor() {
    this.name = 'Angular2'
  }

  firstDropDownChanged(val: any) {
    console.log(val);

    if (val == "1") {
      this._values2 = ["1.1", "1.2", "1.3"];
    }
    else if (val == "2") {
      this._values2 = ["2.1", "2.2", "2.3"];
    }
    else if (val == "3") {
      this._values2 = ["3.1", "3.2", "3.3"];
    }
    else {
      this._values2 = [];
    }
  }
}

live-demo:https://plnkr.co/edit/GDXsPt4aiS7vus6oPvuU？p = preview

UPDATE

或者您可以使用selectedIndex:(注意这-1会导致您的第一个"选择" - 项目.

@Component({
  selector: 'my-app',
  template: `
    <div>
      <h2>Hello {{name}}</h2>

      <select (change)="firstDropDownChanged($event.target.selectedIndex - 1)" >
        <option>Select</option>
        <option *ngFor="let v of _values1">{{ v.val }}</option>
      </select>

      <select >
        <option>Select</option>
        <option *ngFor='let v of _values2'>{{ v }}</option>
      </select>
    </div>
  `,
})
export class App {
  name:string;

  private _values1 = [
    { id: 1, val: "huhu" },
    { id: 2, val: "val2" },
    { id: 3, val: "yep" },
    { id: 4, val: "cool" }
  ];
  private _values2 = [];

  constructor() {
    this.name = 'Angular2'
  }

  firstDropDownChanged(val: any) {
    const obj = this._values1[val];
    console.log(val, obj);

    if (!obj) return;

    if (obj.id == 1) {
      this._values2 = ["1.1", "1.2", "1.3"];
    }
    else if (obj.id == 2) {
      this._values2 = ["2.1", "2.2", "2.3"];
    }
    else if (obj.id == 3) {
      this._values2 = ["3.1", "3.2", "3.3"];
    }
    else {
      this._values2 = [];
    }
  }
}

live-demo:https://plnkr.co/edit/wugNC6S27FB48EtRN906?p=preview