问如何创建下拉列表并与来自服务器的数据绑定

EN

groupBy(xs, key) {
   return xs.reduce(function (rv, x) {
     (rv[x[key]] = rv[x[key]] || []).push(x);
    return rv;
   }, {});
 }

var model;

getData() {
 var   sampleData = {
  "ArrayOfLocationGroup": {
    "LocationGroup": [
      ...
      ...//Server response data
      ],
    "_xmlns:xsd": "http://www.w3.org/2001/XMLSchema"
  }
 }    

var list = this.sampleData["ArrayOfLocationGroup"]["LocationGroup"];
var formattedList = [];

list.forEach(element => {

  var obj = {  //Make sure your server response data to like this structure
    "Id": element.Id,
    "Name": element.Name,
    "GroupId": element.GroupId.__text,
    "ParentLocationGroup": element.ParentLocationGroup.__text,
    "LgLevel": element.LgLevel.__text,
    "Child" : []
  }
  formattedList.push(obj);
});

var groupDataList = this.groupBy(formattedList, "LgLevel");

var parents = groupDataList[0];
var child = groupDataList[1];
var childOfChild = groupDataList[2];

child.forEach(c => {
  c.Child = childOfChild.filter(x => x.ParentLocationGroup == c.Id);
})

parents.forEach(p => {
  p.Child = child.filter(x => x.ParentLocationGroup == p.Id);
})

this.model = parents;
}

    <ul class="nav site-nav">
     <li class=flyout>
      <a href=#>Dropdown</a>
      <!-- Flyout -->
      <ul class="flyout-content nav stacked">
        <li *ngFor="let parent of model" [class.flyout-alt]="parent.Child.length > 0"><a href=#>{{parent.Name}}</a>
          <ul *ngIf="parent.Child.length > 0" class="flyout-content nav stacked">
            <li *ngFor="let c of parent.Child" [class.flyout-alt]="c.Child.length > 0"><a href=#>{{c.Name}}</a>
              <ul *ngIf="c.Child.length > 0" class="flyout-content nav stacked">
                <li *ngFor="let cc of c.Child" [class.flyout-alt]="cc.Child.length > 0"><a href=#>{{cc.Name}}</a></li>
              </ul>
            </li>
          </ul>
        </li>
      </ul>
    </li>
  </ul>

 var obj = {
    "Id": element.Id,
    "Name": element.Name && element.Name.#text ? element.Name.#text : element.Name,
    "GroupId": element.GroupId && element.GroupId.#text ? element.GroupId.#text : element.GroupId,
    "ParentLocationGroup": element.ParentLocationGroup && element.ParentLocationGroup.#text ? element.ParentLocationGroup.#text : element.ParentLocationGroup,
    "LgLevel": element.LgLevel && element.LgLevel.#text ? element.LgLevel.#text : element.LgLevel,
    "Child" : []
  }

  processData(data) {
    let locationData = data.ArrayOfLocationGroup.LocationGroup;
    let level0 = [];
    let tempMap = {};
    for (let i = 0; i < locationData.length; i++) {
      let currItem = this.getDataObject(locationData[i]);
      if (tempMap[currItem.id] == undefined) {
        tempMap[currItem.id] = currItem;
        if (tempMap[currItem.parentLocationGroup] == undefined) {
          tempMap[currItem.parentLocationGroup] = { children: [] };
        }
        tempMap[currItem.parentLocationGroup].children.push(currItem);
      } else {
        if (tempMap[currItem.id]) {
          currItem.children = tempMap[currItem.id].children;
        }
        tempMap[currItem.id] = currItem;
        if (tempMap[currItem.parentLocationGroup] == undefined) {
          tempMap[currItem.parentLocationGroup] = { children: [] };
        }
        tempMap[currItem.parentLocationGroup].children.push(currItem);
      }
      if (currItem.lgLevel == "0") {
        if (level0.indexOf(currItem) == -1) {
          level0.push(currItem);
        }
      }
    }
    this.levelData = level0;
  }

export interface GroupId { /* appropriate members... */ }

export interface ParentLocationGroup { /* other members... */ __text: string; }

export interface LgLevel { /* other members... */ __text: string; }

export interface DataModel {
  Id: string,
  Name: string,
  GroupId: GroupId,
  ParentLocationGroup: ParentLocationGroup,
  LgLevel: LgLevel,
  children: DataModel[]
}

// dropdown.component.ts

@Component({
  selector: 'app-dropdown',
  template: `
    <ul class="nav site-nav">
      <li class=flyout>
        <a href=#>Dropdown</a>
        <app-dynamic-flyout [data]="data"></app-dynamic-flyout>
      </li>
    </ul>
  `
})
export class DropdownComponent {

  data: DataModel[];

  constructor(dataService: YourDataService){

    let data;
    dataService.getYourData()
      .pipe(map(d => d.ArrayOfLocationGroup.LocationGroup)))
      // Make sure every item has the `children` array property initialized
      // since it does not come with your data
      .subscribe(d => data = d.map(i => ({...i, children: []})));

    // Create a lookup map for building the data tree
    let idMap = data.reduce((acc, curr) => ({...acc, [curr.Id]: curr}), {});
    this.data = data.reduce(
      (acc, curr) => curr.LgLevel.__text == 0 || !curr.ParentLocationGroup
        // Either the level is 0 or there is no parent group
        // (the logic is unclear here - even some of your lvl 0 nodes have a `ParentGroup`)
        // -> we assume this is a top-level node and put it to the accumulator
        ? [...acc, curr]
        // Otherwise push this node to an appropriate `children` array
        // and return the current accumulator
        : idMap[curr.ParentLocationGroup.__text].children.push(curr) && acc, 
      []
    );
  }
}

// dynamic-flyout.component.ts

@Component({
  selector: 'app-dynamic-flyout',
  template: `
    <ul *ngIf="!!data.length" class="flyout-content nav stacked">
      <li *ngFor="let item of data" [class.flyout-alt]="!!item.children.length">
        <a href=#>{{item.Name}}</a>
        <app-dynamic-flyout [data]="item.children"></app-dynamic-flyout>
      </li>
    </ul>
  `
})
export class DynamicFlyoutComponent {
  @Input() data: DataModel[];
}