Angular利用内容投射向组件输入ngForOf模板的方法

2019-11-19 14:14:13

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现在，我们写一个组件puppiesListCmp，用于显示小狗狗的列表：

//puppies-list.component.ts@Component({ selector: 'puppies-list', template: `  <div *ngFor="let puppy of puppies">   <span>{{puppy.name}}</span>   <span>{{puppy.age}}</span>   <span>{{puppy.color}}</span>  </div>`})export class puppiesListCmp{ @Input() puppies: Puppy[];}interface Puppy { name: string, age: number, color: string}

然后这样使用：

//app.component.ts@Component({ selector: 'my-app', template: `  <puppies-list [puppies]="puppies"></puppies-list>`})export class App{ puppies = [  {   name: "sam",   age: 0.6,   color: "yellow"  },  {   name: "bingo",   age: 1.5,   color: "black"  } ]}

效果就行这样：

但是，我希望我们的puppiesListCmp组件可以满足不同的需求，比如在数据不变的情况下只显示小狗狗的name和color，就像这样：

这就是本文的重点了。我们需要实现用户自定义模板！

现在我们不写死组件的模板了，而是让用户从外部输入!

首先，我们的组件模板：

<div *ngFor="let puppy of puppies">   <span>{{puppy.name}}</span>   <span>{{puppy.age}}</span>   <span>{{puppy.color}}</span></div>

等价于：

<ng-template ngFor let-puppy [ngForOf]="puppies">   <div>    <span>{{puppy.name}}</span>    <span>{{puppy.age}}</span>    <span>{{puppy.color}}</span>   </div></ng-template>

然后，用@ContentChild（关于@ContentChild可以查看这里，需FQ）获取到外部（相对puppiesListCmp组件而言）自定义模板，并赋给ngForTemplate。也就是说，这部分：

<div>  <span>{{puppy.name}}</span>  <span>{{puppy.age}}</span>  <span>{{puppy.color}}</span></div>

不再像之前那样写死在组件里了，而是由使用者在父组件中自定义，然后利用Angular的内容投射（Content Projection），投射到puppiesListCmp组件里面。就像这样：

//puppies-list.component.tsimport { Component, Input, ContentChild, TemplateRef } from '@angular/core';import { NgForOfContext } from '@angular/common';@Component({ selector: 'puppies-list', template: `<ng-template ngFor let-puppy [ngForOf]="puppies" [ngForTemplate]="tpl"></ng-template>`})export class puppiesListCmp{ @Input() puppies: Puppy[]; @ContentChild(TemplateRef) tpl: TemplateRef<NgForOfContext<Puppy>>}interface Puppy { name: string, age: number, color: string}

这样我们的组件就算完成了。然后我们使用它：

//app.component.ts@Component({ selector: 'my-app', template: `<puppies-list [puppies]="puppies"> <ng-template let-puppy>  <div>   <span>{{puppy.name}}</span>   <span>{{puppy.age}}</span>   <span>{{puppy.color}}</span>  </div> </ng-template></puppies-list>`})

效果还是一样的：

如果我们只要显示小狗狗的name和color，只要这样写就好了：

//app.component.ts@Component({ selector: 'my-app', template: `<puppies-list [puppies]="puppies"> <ng-template let-puppy>  <div>   <span>{{puppy.name}}</span>   <span>{{puppy.color}}</span>  </div> </ng-template></puppies-list>`})

效果就像这样：