为什么 *ngIf 不适用于 ng-template? [英] why *ngIf doesnt'work with ng-template?

问题描述

我在模板中有一个条件如下:

<p *ngFor="让 InfoDetails 的座位?.seatInfo"><模板 *ngIf="seat.section">部分 {{seat?.section}} ,<模板 *ngIf="seat.row">第 {{seat?.row}},<模板 *ngIf="seat.seatNo">座位号{{seat?.seatNo}}</p></ng-容器>

我有包含 row 和 seatNo 的数据集，但它似乎没有在模板中打印.这里有什么问题?

解决方案

在此处阅读文档 https://angular.io/guide/structural-directives 特别适用于

<块引用>

<div *ngIf="hero" >{{hero.name}}</div>

星号是多一点的语法糖"复杂的.在内部，Angular 分两个阶段对其进行脱糖.首先，它将 *ngIf="..." 转换为模板属性，template="ngIf..."，就像这样.

{{hero.name}}

然后它把模板属性翻译成一个元素，包裹在宿主元素上，像这样.

<div>{{hero.name}}</div></ng-template>

• *ngIf 指令移动到元素，在那里它成为一个属性绑定，[ngIf].
• 的其余部分，包括它的 class 属性，移动到元素内部.

所以我们有 ng-container

 部分 {{seat.section}} ,</ng-容器>

或使用 span 或 div 或常规 html 标签.

 部分 {{seat.section}} ,</span>

或者如果你仍然想使用 ng-template (不推荐)

部分 {{seat.section}} ,</ng-模板>

I have a condition in the template as follows:

<ng-container>
    <p *ngFor="let seat of InfoDetails?.seatInfo">
        <template *ngIf="seat.section">
            Section {{seat?.section}} ,
        </template>
        <template *ngIf="seat.row">
            Row {{seat?.row}},
        </template>
        <template *ngIf="seat.seatNo">
            Seat number {{seat?.seatNo}}
        </template>
    </p>
</ng-container>

I have dataset that contains row and seatNo, but it does not seem to print in the template. what is the issue here?

解决方案

Read the doc here https://angular.io/guide/structural-directives especially for

<div *ngIf="hero" >{{hero.name}}</div>

The asterisk is "syntactic sugar" for something a bit more complicated. Internally, Angular desugars it in two stages. First, it translates the *ngIf="..." into a template attribute, template="ngIf ...", like this.

<div template="ngIf hero">{{hero.name}}</div>

Then it translates the template attribute into a element, wrapped around the host element, like this.

<ng-template [ngIf]="hero"> <div>{{hero.name}}</div></ng-template>

• The *ngIf directive moved to the element where it became a property binding,[ngIf].
• The rest of the , including its class attribute, moved inside the element.

So for it we have ng-container

 <ng-container *ngIf="seat.section">
    Section {{seat.section}} ,
 </ng-container>

or use span or div or regular html tag.

 <span *ngIf="seat.section">
    Section {{seat.section}} ,
 </span>

or if you still want to use ng-template (not recommended)

<ng-template [ngIf]="seat.section">
  Section {{seat.section}} ,
</ng-template>

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