How would I have multiple cases in an *ngIf
statement? I'm used to Vue or Angular 1 with having an if
, else if
, and else
, but it seems like Angular 4 only has a true
(if
) and false
(else
) condition.
According to the documentation, I can only do:
<ng-container *ngIf="foo === 1; then first else second"></ng-container>
<ng-template #first>First</ng-template>
<ng-template #second>Second</ng-template>
<ng-template #third>Third</ng-template>
But I want to have multiple conditions (something like):
<ng-container *ngIf="foo === 1; then first; foo === 2; then second else third"></ng-container>
<ng-template #first>First</ng-template>
<ng-template #second>Second</ng-template>
<ng-template #third>Third</ng-template>
But I'm ending up having to use ngSwitch
, which feels like a hack:
<ng-container [ngSwitch]="true">
<div *ngSwitchCase="foo === 1">First</div>
<div *ngSwitchCase="bar === 2">Second</div>
<div *ngSwitchDefault>Third</div>
</ng-container>
Alternately, it seems like a lot of the syntaxes I've got used to from Angular 1 and Vue aren't supported in Angular 4, so what would be the recommended way to structure my code with conditions like this?
This question is related to
angular
templates
angular-ng-if
You can also use this old trick for converting complex if/then/else blocks into a slightly cleaner switch statement:
<div [ngSwitch]="true">
<button (click)="foo=(++foo%3)+1">Switch!</button>
<div *ngSwitchCase="foo === 1">one</div>
<div *ngSwitchCase="foo === 2">two</div>
<div *ngSwitchCase="foo === 3">three</div>
</div>
You can use multiple way based on sitaution:
If you Variable is limited to specific Number or String, best way is using ngSwitch or ngIf:
<!-- foo = 3 -->
<div [ngSwitch]="foo">
<div *ngSwitchCase="1">First Number</div>
<div *ngSwitchCase="2">Second Number</div>
<div *ngSwitchCase="3">Third Number</div>
<div *ngSwitchDefault>Other Number</div>
</div>
<!-- foo = 3 -->
<ng-template [ngIf]="foo === 1">First Number</ng-template>
<ng-template [ngIf]="foo === 2">Second Number</ng-template>
<ng-template [ngIf]="foo === 3">Third Number</ng-template>
<!-- foo = 'David' -->
<div [ngSwitch]="foo">
<div *ngSwitchCase="'Daniel'">Daniel String</div>
<div *ngSwitchCase="'David'">David String</div>
<div *ngSwitchCase="'Alex'">Alex String</div>
<div *ngSwitchDefault>Other String</div>
</div>
<!-- foo = 'David' -->
<ng-template [ngIf]="foo === 'Alex'">Alex String</ng-template>
<ng-template [ngIf]="foo === 'David'">David String</ng-template>
<ng-template [ngIf]="foo === 'Daniel'">Daniel String</ng-template>
Above not suitable for if elseif else codes and dynamic codes, you can use below code:
<!-- foo = 5 -->
<ng-container *ngIf="foo >= 1 && foo <= 3; then t13"></ng-container>
<ng-container *ngIf="foo >= 4 && foo <= 6; then t46"></ng-container>
<ng-container *ngIf="foo >= 7; then t7"></ng-container>
<!-- If Statement -->
<ng-template #t13>
Template for foo between 1 and 3
</ng-template>
<!-- If Else Statement -->
<ng-template #t46>
Template for foo between 4 and 6
</ng-template>
<!-- Else Statement -->
<ng-template #t7>
Template for foo greater than 7
</ng-template>
Note: You can choose any format, but notice every code has own problems
This seems to be the cleanest way to do
if (foo === 1) {
} else if (bar === 99) {
} else if (foo === 2) {
} else {
}
in the template:
<ng-container *ngIf="foo === 1; else elseif1">foo === 1</ng-container>
<ng-template #elseif1>
<ng-container *ngIf="bar === 99; else elseif2">bar === 99</ng-container>
</ng-template>
<ng-template #elseif2>
<ng-container *ngIf="foo === 2; else else1">foo === 2</ng-container>
</ng-template>
<ng-template #else1>else</ng-template>
Notice that it works like a proper else if
statement should when the conditions involve different variables (only 1 case is true at a time). Some of the other answers don't work right in such a case.
aside: gosh angular, that's some really ugly else if
template code...
you don't need to use *ngIf if you use ng-container
<ng-container [ngTemplateOutlet]="myTemplate === 'first' ? first : myTemplate ===
'second' ? second : third"></ng-container>
<ng-template #first>first</ng-template>
<ng-template #second>second</ng-template>
<ng-template #third>third</ng-template>
Or maybe just use conditional chains with ternary operator. if … else if … else if … else
chain.
<ng-container *ngIf="isFirst ? first: isSecond ? second : third"></ng-container>
<ng-template #first></ng-template>
<ng-template #second></ng-template>
<ng-template #third></ng-template>
I like this aproach better.
You can just use:
<ng-template [ngIf]="index == 1">First</ng-template>
<ng-template [ngIf]="index == 2">Second</ng-template>
<ng-template [ngIf]="index == 3">Third</ng-template>
unless the ng-container part is important to your design I suppose.
Here's a Plunker
To avoid nesting and ngSwitch, there is also this possibility, which leverages the way logical operators work in Javascript:
<ng-container *ngIf="foo === 1; then first; else (foo === 2 && second) || (foo === 3 && third)"></ng-container>
<ng-template #first>First</ng-template>
<ng-template #second>Second</ng-template>
<ng-template #third>Third</ng-template>
<ion-row *ngIf="cat === 1;else second"></ion-row>_x000D_
<ng-template #second>_x000D_
<ion-row *ngIf="cat === 2;else third"></ion-row>_x000D_
</ng-template>_x000D_
<ng-template #third>_x000D_
_x000D_
</ng-template>
_x000D_
Angular is already using ng-template under the hood in many of the structural directives that we use all the time: ngIf, ngFor and ngSwitch.
> What is ng-template in Angular
https://www.angularjswiki.com/angular/what-is-ng-template-in-angular/
Source: Stackoverflow.com