使用 ng-template

如何解决使用 ng-template

我认为这很简单，但由于某种原因我无法弄清楚。 我正在构建一个简单的子菜单。我已经创建了组件：

export class SubMenuComponent implements OnInit {
    @input() links: MenuItem[];

    constructor() {}

    ngOnInit(): void {}
}

MenuItem 看起来像这样：

export class MenuItem {
    label: string;
    path: string;
    open: boolean;
    children?: MenuItem[];
}

Html 如下所示：

<ul class="app-sub-menu list-unstyled">
    <li *ngFor="let link of links" routerLinkActive="active"><a class="btn-link" [routerLink]="link.path"
            routerLinkActive="active" [routerLinkActiveOptions]="{exact: link.path === '/'}">{{ link.label }}</a>

        <span class="toggle" *ngIf="link.children?.length" (click)="link.open = !link.open">
            <mat-icon *ngIf="link.isActive || link.open">keyboard_arrow_down</mat-icon>
            <mat-icon *ngIf="!link.isActive && !link.open">keyboard_arrow_up</mat-icon>
        </span>

        <ul class="list-unstyled" [class.open]="link.open" *ngIf="link.children?.length">
            <li *ngFor="let link of link.children" routerLinkActive="active"><a class="btn-link"
                    routerLinkActive="active" [routerLink]="link.path" #link>{{ link.label }}</a>

                <span class="toggle" *ngIf="link.children?.length" (click)="link.open = !link.open">
                    <mat-icon *ngIf="link.isActive || link.open">keyboard_arrow_down</mat-icon>
                    <mat-icon *ngIf="!link.isActive && !link.open">keyboard_arrow_up</mat-icon>
                </span>

                <ul class="list-unstyled" [class.open]="link.open" *ngIf="link.children?.length">
                    <li *ngFor="let link of link.children" routerLinkActive="active"><a class="btn-link"
                            routerLinkActive="active" [routerLink]="link.path">{{ link.label }}</a>
                    </li>
                </ul>
            </li>
        </ul>
    </li>
</ul>

如您所见，当前的子菜单仅下降了 3 个级别。我希望它是无限嵌套的。 所以我决定使用 ng-template，但我无法让它工作。 我认为这会很简单：

<ul class="app-sub-menu list-unstyled">
    <ng-template *ngTemplateOutlet="link" *ngFor="let link of links"></ng-template>
</ul>

<ng-template #link>
    <li *ngFor="let link of links" routerLinkActive="active"><a class="btn-link" [routerLink]="link.path"
            routerLinkActive="active" [routerLinkActiveOptions]="{exact: link.path === '/'}">{{ link.label }}</a>

        <span class="toggle" *ngIf="link.children?.length" (click)="link.open = !link.open">
            <mat-icon *ngIf="link.isActive || link.open">keyboard_arrow_down</mat-icon>
            <mat-icon *ngIf="!link.isActive && !link.open">keyboard_arrow_up</mat-icon>
        </span>

        <ul class="list-unstyled" [class.open]="link.open" *ngIf="link.children?.length">
            <ng-template *ngTemplateOutlet="link" *ngFor="let link of link.children"></ng-template>
        </ul>
    </li>
</ng-template>

但是当我尝试使用它时，出现错误：

不能在一个元素上有多个模板绑定。只使用一个带有 *

前缀的属性

所以我改成这样：

现在我收到一个新错误：

templateRef.createEmbeddedView 不是函数

有谁知道我能做些什么来让它发挥作用？

---

阅读：

https://medium.com/@nehaabrol87/the-power-of-angulars-ngtemplateoutlet-used-to-implement-a-nested-data-structure-11c741e6b48c

看起来我的模板使用不正确，所以我将其更改为：

<ul class="app-sub-menu list-unstyled">
    <ng-container *ngTemplateOutlet="link; context: { $implicit: links }"></ng-container>
</ul>

<ng-template #link let-links>
    <li *ngFor="let link of links" routerLinkActive="active"><a class="btn-link" [routerLink]="link.path"
            routerLinkActive="active" [routerLinkActiveOptions]="{exact: link.path === '/'}">{{ link.label }}</a>

        <span class="toggle" *ngIf="link.children?.length" (click)="link.open = !link.open">
            <mat-icon *ngIf="link.isActive || link.open">keyboard_arrow_down</mat-icon>
            <mat-icon *ngIf="!link.isActive && !link.open">keyboard_arrow_up</mat-icon>
        </span>

        <ul class="list-unstyled" [class.open]="link.open" *ngIf="link.children?.length">
            <ng-container *ngTemplateOutlet="link; context: { $implicit: link.children }"></ng-container>
        </ul>
    </li>
</ng-template>

但我仍然收到错误:(

templateRef.createEmbeddedView 不是函数

解决方法

我想通了，这是因为我的模板ID与实际模型相同。所以我改成这样：

<ul class="app-sub-menu list-unstyled">
    <ng-template #nestedList let-links>
        <li *ngFor="let link of links" routerLinkActive="active"><a class="btn-link" [routerLink]="link.path"
                routerLinkActive="active" [routerLinkActiveOptions]="{exact: link.path === '/'}">{{ link.label }}</a>

            <span class="toggle" *ngIf="link.children?.length" (click)="link.open = !link.open">
                <mat-icon *ngIf="link.isActive || link.open">keyboard_arrow_down</mat-icon>
                <mat-icon *ngIf="!link.isActive && !link.open">keyboard_arrow_up</mat-icon>
            </span>

            <ul class="list-unstyled" [class.open]="link.open" *ngIf="link.children?.length">
                <ng-container *ngTemplateOutlet="nestedList; context: { $implicit: link.children }"></ng-container>
            </ul>
        </li>
    </ng-template>
    <ng-container *ngTemplateOutlet="nestedList; context: { $implicit: links }"></ng-container>
</ul>