Angular利用內容投射向組件輸入ngForOf模板的方法

2019-11-19 14:14:13

字體：大中小

來源：轉載

供稿：網友

現在，我們寫一個組件puppiesListCmp，用于顯示小狗狗的列表：

//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}

然后這樣使用：

//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"  } ]}

效果就行這樣：

但是，我希望我們的puppiesListCmp組件可以滿足不同的需求，比如在數據不變的情況下只顯示小狗狗的name和color，就像這樣：

這就是本文的重點了。我們需要實現用戶自定義模板！

現在我們不寫死組件的模板了，而是讓用戶從外部輸入!

首先，我們的組件模板：

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

等價于：

<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（關于@ContentChild可以查看這里，需FQ）獲取到外部（相對puppiesListCmp組件而言）自定義模板，并賦給ngForTemplate。也就是說，這部分：

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

不再像之前那樣寫死在組件里了，而是由使用者在父組件中自定義，然后利用Angular的內容投射（Content Projection），投射到puppiesListCmp組件里面。就像這樣：

//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}

這樣我們的組件就算完成了。然后我們使用它：

//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>`})

效果還是一樣的：

如果我們只要顯示小狗狗的name和color，只要這樣寫就好了：

//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>`})

效果就像這樣：