Angular @ViewChild() error: Expected 2 arguments, but got 1

Question

When trying ViewChild I am getting the error. Error is \"An argument for \'opts\' was not provided.\"

Both @ViewChild is giving the error.

Answer 1

Angular 8

In Angular 8, ViewChild has another param

@ViewChild('nameInput', {static: false}) component : Component

You can read more about it here and here

Angular 9 & Angular 10

In Angular 9 default value is static: false, so doesn't need to provide param unless you want to use {static: true}

Answer 2

In Angular 8 , ViewChild takes 2 parameters:

Try like this:

@ViewChild('nameInput', { static: false }) nameInputRef: ElementRef;

Explanation:

{ static: false }

If you set static false, the child component ALWAYS gets initialized after the view initialization in time for the ngAfterViewInit/ngAfterContentInit callback functions.

{ static: true}

If you set static true, the child component initialization will take place at the view initialization at ngOnInit

By default you can use { static: false }. If you are creating a dynamic view and want to use the template reference variable, then you should use { static: true}

For more info, you can read this article

Working Demo

In the demo, we will scroll to a div using template reference variable.

 @ViewChild("scrollDiv", { static: true }) scrollTo: ElementRef;

With { static: true }, we can use this.scrollTo.nativeElement in ngOnInit, but with { static: false }, this.scrollTo will be undefined in ngOnInit , so we can access in only in ngAfterViewInit

Answer 3

you should use second argument with ViewChild like this:

@ViewChild("eleDiv", { static: false }) someElement: ElementRef;

Answer 4

In Angular 8 , ViewChild takes 2 parameters

 @ViewChild(ChildDirective, {static: false}) Component

Answer 5

it is because view child require two argument try like this

@ViewChild('nameInput', { static: false, }) nameInputRef: ElementRef;

@ViewChild('amountInput', { static: false, }) amountInputRef: ElementRef;

Answer 6

Regex for replacing all via IDEA (tested with Webstorm)

Find: \@ViewChild\('(.*)'\)

Replace: \@ViewChild\('$1', \{static: true\}\)