如何放置AngularJS 2中选择的选项？

Question

我试图弄清楚如何在显示时选择一个选项，使用旧的javascript风格代码或其他语言，例如：

<select>
for (x =0 ; x < elements.size ; x++) {
<option value="element.id" if (element.id == selected.id ) print selected (endif)>element.name</option>
}
</select>

在angularjs中尝试这样做时，我最终得到了类似下面所示的东西。

这是代码：

import { Component } from '@angular/core';

export class Category {
    id: number;
    name: String;
    parent_id: number;
}

const CATEGORIES: Category[] = [
    {id: 1, name: "Calças", parent_id: 0},
    {id: 2, name: "Calças de ganga", parent_id: 1},
    {id: 3, name: "Calças Moleton", parent_id: 1},
    {id: 4, name: "T-shirt", parent_id: 0},
    {id: 5, name: "Casaco", parent_id: 0},
    {id: 6, name: "Casaco Moleton", parent_id: 5},
    {id: 7, name: "Sapato", parent_id: 0},
    {id: 8, name: "Ténis", parent_id: 7},
    {id: 9, name: "Sapato senhora", parent_id: 7},
    {id: 10, name: "Cintos", parent_id: 0},
];

@Component({
  template: `
  This is the category page.
  Procurar:&nbsp;<input type="text" name="search" />
  <button >Procurar</button>

  <table class="table table-bordered table-hover">
    <tr>
    <th>Id</th>
    <th>Nome</th>
    <th>Categoria Pai</th>
    </tr>
    <tr *ngFor="let cat of categories" (click)="onSelect(cat)">
        <td>{{cat.id}}</td>
        <td><input type="text" value="{{cat.name}}" /></td>
        <td>
            <select>
            <option value="0">&nbsp;</option>
                <option *ngFor="let parent of categories" 
                value="{{parent.id}}">
                    {{parent.name}}
                </option>
            </select>
        </td>
    </tr>
    </table>

  `
})

export class CategoryComponent  { 
    categories = CATEGORIES;

    parents : Category[];

    selectedCategory: Category;

    onSelect(cat: Category): void {
        this.selectedCategory = cat;
    }

    parentCategories() : Category[] {
        var parents : Category[];
        for (let cat of this.categories ) {
            if (cat.parent_id == 0 ) {
                parents.push(cat);
            }
        }
        return parents;
    }
}

如何才能正确地执行此操作？

Answer 1

将[（ngModel）]=“selectedValue”添加到您的选择中？引用角度文档：

<select class="form-control"  id="power"
      required
      [(ngModel)]="model.power" name="power">
  <option *ngFor="let pow of powers" [value]="pow">{{pow}}</option>
</select>