我使用的是Angular,我想在这个例子中使用*ngIf else(从版本4开始可用):
<div *ngIf="isValid">
content here ...
</div>
<div *ngIf="!isValid">
other content here...
</div>
我怎样才能用ngIf else实现同样的行为?
我使用的是Angular,我想在这个例子中使用*ngIf else(从版本4开始可用):
<div *ngIf="isValid">
content here ...
</div>
<div *ngIf="!isValid">
other content here...
</div>
我怎样才能用ngIf else实现同样的行为?
当前回答
在Angular 4、5和6中
我们可以简单地创建一个模板引用变量2,并将其链接到*ngIf指令中的else条件
可能的语法是:
<!-- Only If condition -->
<div *ngIf="condition">...</div>
<!-- or -->
<ng-template [ngIf]="condition"><div>...</div></ng-template>
<!-- If and else conditions -->
<div *ngIf="condition; else elseBlock">...</div>
<!-- or -->
<ng-template #elseBlock>...</ng-template>
<!-- If-then-else -->
<div *ngIf="condition; then thenBlock else elseBlock"></div>
<ng-template #thenBlock>...</ng-template>
<ng-template #elseBlock>...</ng-template>
<!-- If and else conditions (storing condition value locally) -->
<div *ngIf="condition as value; else elseBlock">{{value}}</div>
<ng-template #elseBlock>...</ng-template>
演示: https://stackblitz.com/edit/angular-feumnt?embed=1&file=src/app/app.component.html
来源:
NgIf -指令 模板的语法
其他回答
Angular 4和Angular 5:
使用其他:
<div *ngIf="isValid;else other_content">
content here ...
</div>
<ng-template #other_content>other content here...</ng-template>
你也可以用then else:
<div *ngIf="isValid;then content else other_content">here is ignored</div>
<ng-template #content>content here...</ng-template>
<ng-template #other_content>other content here...</ng-template>
或者独自一人:
<div *ngIf="isValid;then content"></div>
<ng-template #content>content here...</ng-template>
演示:
砰砰作响
细节:
<ng-template>:是Angular自己对<template>标签的实现,根据MDN:
HTML <template>元素是一种保存客户端的机制 加载页面时不呈现但可以呈现的内容 然后在运行时使用JavaScript实例化。
在Angular 4.0中,if..else语法非常类似于Java中的条件操作符。
在Java中,你使用“条件?stmnt1:stmnt2”。
在Angular 4.0中,你使用*ngIf="condition;then stmnt1 else stmnt2"。
ngIf/Else的语法
<div *ngIf=”condition; else elseBlock”>Truthy condition</div>
<ng-template #elseBlock>Falsy condition</ng-template>
使用NgIf / Else/ Then显式语法
要添加then模板,只需显式地将其绑定到模板。
<div *ngIf=”condition; then thenBlock else elseBlock”> ... </div>
<ng-template #thenBlock>Then template</ng-template>
<ng-template #elseBlock>Else template</ng-template>
NgIf和Async Pipe的可观察对象
欲知详情
只需从Angular 8中添加新的更新。
For case if with else, we can use ngIf and ngIfElse. <ng-template [ngIf]="condition" [ngIfElse]="elseBlock"> Content to render when condition is true. </ng-template> <ng-template #elseBlock> Content to render when condition is false. </ng-template> For case if with then, we can use ngIf and ngIfThen. <ng-template [ngIf]="condition" [ngIfThen]="thenBlock"> This content is never showing </ng-template> <ng-template #thenBlock> Content to render when condition is true. </ng-template> For case if with then and else, we can use ngIf, ngIfThen, and ngIfElse. <ng-template [ngIf]="condition" [ngIfThen]="thenBlock" [ngIfElse]="elseBlock"> This content is never showing </ng-template> <ng-template #thenBlock> Content to render when condition is true. </ng-template> <ng-template #elseBlock> Content to render when condition is false. </ng-template>
ng-template
<ng-template [ngIf]="condition1" [ngIfElse]="template2">
...
</ng-template>
<ng-template #template2>
...
</ng-template>