Ein Artikel zum Verständnis der drei Arten der Inhaltsprojektion in Angular (Single-Slot, Multi-Slot, bedingt)

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

@Component({
  selector: 'app-zippy-basic',
  template: `
  <h2>单插槽内容投影</h2>
  <ng-content></ng-content>
`
})
export class ZippyBasicComponent {}

<!-- 将 app-zippy-basic 元素包裹的全部内容投影到 zippy-basic 组件中去 -->
<app-zippy-basic>
  <p>单插槽内容投影：投影数据</p>
</app-zippy-basic>

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

@Component({
  selector: 'app-zippy-multislot',
  template: `
  <h2>多插槽内容投影</h2>
  <ng-content></ng-content>
  <ng-content select="[question]"></ng-content>
`
})
export class ZippyMultislotComponent {}

<!-- 使用 question 属性的内容将投影到带有 `select=[question]` 属性的 ng-content 元素。 -->
<app-zippy-multislot>
  <p question style="color: hotpink;">
    带question属性的p元素
  </p>
  <p style="color: lightgreen">不带question属性的p元素-->匹配到不带select属性的ng-content</p>
  <p>不带question属性的p元素-->匹配到不带select属性的ng-content</p>
</app-zippy-multislot>

<ng-container *ngTemplateOutlet="templateRefExp; context: contextExp"></ng-container>
<!-- 等同 -->
<ng-container [ngTemplateOutlet]="templateRefExp" [ngTemplateOutletContext]="contextExp"></ng-container>

<header>头部</header>
<main>
	<h3>内容：</h3>
	<ng-container [ngTemplateOutlet]="greet"></ng-container>
</main>
<footer>底部</footer>

<ng-template #greet>
	<div>
		<h4>hi!</h4>
		<h4>hello my dear friend!</h4>
	</div>
</ng-template>

/**** part-b.component.ts ****/
import { Component, OnInit,Output} from '@angular/core';

@Component({
	selector: 'app-content-part-b',
	templateUrl: './part-b.component.html',
	styleUrls: ['./part-b.component.scss']
})

export class PartBComponent implements OnInit {
	constructor() { }
	ngOnInit() { }
	
	public func():void{
		console.log("PartB");
	} 
}

/**** part-a.component.ts ****/
import { Component, OnInit, ContentChild } from '@angular/core';
// 1、引入 part-b 组件
import { PartBComponent } from '../part-b/part-b.component';

@Component({
	selector: 'app-content-part-a',
	templateUrl: './part-a.component.html',
	styleUrls: ['./part-a.component.scss']
})

export class PartAComponent implements OnInit {
	// 2、获取投影
	@ContentChild(PartBComponent) PartB:PartBComponent
	constructor() { }
	ngOnInit() {}
	ngAfterContentInit(): void {
		// 3、调用 part-b 组件的 func() 方法
		this.PartB.func();
	}
	public func() {
		console.log('PartA')
	}
}

 <!-- content.component.html -->
<div>
	<div>Content</div>
	<div>
		<app-content-part-a>
		<!-- 投影在part-a组件中的内容 -->
			<h1>PartA--start</h1>
			<app-content-part-b></app-content-part-b>
			<span>PartA--end</span>
		</app-content-part-a>
	</div>
</div>

 <!-- content.component.html -->
<div>
	<div>Content</div>
	<div>
	<!-- 在此处引用模板变量 #partA -->
		<app-content-part-a #partA>
			<h1>PartA--start</h1>
				<app-content-part-b></app-content-part-b>
			<span>PartA--end</span>
		</app-content-part-a>
	</div>
</div>

/**** content.component.ts ****/
import { Component, OnInit, ViewChild } from '@angular/core';

@Component({
	selector: 'app-content',
	templateUrl: './content.component.html',
	styleUrls: ['./content.component.scss']
})

export class ContentComponent implements OnInit {
	// 2、获取视图 partA
	@ViewChild('partA') partA: any;
	constructor() { }
	ngOnInit() {}
	ngAfterViewInit(): void {
		// 3、调用 part-a 组件的 func() 方法
		this.partA.func();
	}
}

import { Component, OnInit, ContentChild,ContentChildren ,QueryList } from '@angular/core';
import { PartBComponent } from '../part-b/part-b.component';

@Component({
	selector: 'app-content-part-a',
	templateUrl: './part-a.component.html',
	styleUrls: ['./part-a.component.scss']
})
export class PartAComponent implements OnInit {

	@ContentChildren(PartBComponent) PartBs: QueryList<PartBComponent>;

	constructor() { }
	ngOnInit() {}
}