*ngIf else if in template
AngularTemplatesAngular Ng-IfAngular Problem Overview
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?
Angular Solutions
Solution 1 - Angular
Another alternative is to nest conditions
<ng-container *ngIf="foo === 1;else second"></ng-container>
<ng-template #second>
<ng-container *ngIf="foo === 2;else third"></ng-container>
</ng-template>
<ng-template #third></ng-template>
Solution 2 - Angular
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
Solution 3 - Angular
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...
Solution 4 - Angular
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
Solution 5 - Angular
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>
Solution 6 - Angular
Or maybe just use conditional chains with ternary operator. if … else if … else if … else
chain.
<ng-container [ngTemplateOutlet]="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.
Solution 7 - Angular
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>
Solution 8 - Angular
<ion-row *ngIf="cat === 1;else second"></ion-row>
<ng-template #second>
<ion-row *ngIf="cat === 2;else third"></ion-row>
</ng-template>
<ng-template #third>
</ng-template>
> 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/
Solution 9 - Angular
I came a cross this type of situation *ngIf elseIf else
and I solved using ng-template
, Hope the following snippet may depicts briefly,
I have a form control named "NIC" and need to show one error message at a time when the form control invalid.
form: FormGroup = new FormGroup({
NIC: new FormControl('', [Validators.required, Validators.minLength(10), Validators.maxLength(10), Validators.pattern("^[0-9]*$")])
});
Template
<mat-form-field appearance="standard">
<mat-label>NIC Number</mat-label>
<input matInput placeholder="Enter NIC no" formControlName="NIC">
<mat-error *ngIf="form.controls['NIC'].errors?.required; else minvalue">This field is mandatory.
</mat-error>
<ng-template #minvalue>
<mat-error *ngIf="form.controls['NIC'].errors?.minlength; else maxvalue">Minimum 10 charactors
needed.
</mat-error>
</ng-template>
<ng-template #maxvalue>
<mat-error *ngIf="form.controls['NIC'].errors?.maxLength; else numericonly">Maximum 10
charactors allowed.
</mat-error>
</ng-template>
<ng-template #numericonly>
<mat-error *ngIf="form.controls['NIC'].errors?.pattern">
Numeric characters only.
</mat-error>
</ng-template>
</mat-form-field>
Solution 10 - Angular
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>