What Is a Template Reference Variable?
A template reference
variable is a way of capturing a reference to a specific element, component, directive,
and pipe so that it can be used someplace in the same template HTML.
You should declare a
reference variable using the hash symbol (#).
The Angular components
and directives only match selectors for classes that are declared in the
Angular module.
Template
Reference Variable Syntax –
You can use a
template reference variable by two ways.
1. Using
hash symbol (#)
2. Using
reference symbol (ref-)
The
following examples of specifying a template reference variable using Input Text
Box –
I have declared a
reference variable “cellnumber” using the hash
symbol (#) and reference symbol
(ref-).
<input
type="text"
ref-cellnumber> //cellnumber
will be a template reference variable.
And
<input
#cellnumber placeholder="Cell
number"> //cellnumber
will be a template reference variable.
I have created a
reference to the input element that can be used later on in my template and the
scope for “cellnumber” variable is
the entire HTML template in which the reference is defined.
Here is how I could
use that reference to get the value of the input for instance –
//cellnumber refers to the input
element
<button
(click)="show(cellnumber)">click
to see</button>
In the below line of
code, the variable “cellnumber” refer to the HTMLElement object instance for
the input -
show(cellnumber:
HTMLInputElement){
console.log(cellnumber.value);
}
You can use the ViewChild
decorator to reference it inside your component.
import
{ViewChild, ElementRef}
from '@angular/core';
// Reference cellnumber variable
inside Component
@ViewChild('cellnumber')
cellInputRef: ElementRef;
And finally, you can
use this.nameInputRef anywhere inside your component class.
show(){
this.contactNumber
= this.cellInputRef.nativeElement.value
}
Template
Reference Variable with NgForm –
Here we will discuss
about how to access NgForm directive using template reference variable.
<form
(ngSubmit)="onSubmitEmployee(empForm)"
#empForm="ngForm">
<label>F-Name
</label><input
name="f-name"
required [(ngModel)]="employee.fname">
<label>L-Name
</label><input
name="l-name"
required [(ngModel)]="employee.lname">
<label>Age </label><input
name="age"
required [(ngModel)]="employee.age">
<button
type="submit"
[disabled]="!empForm.form.valid">Submit</button>
</form>
In the above NgForm example
contains an ngSubmit event and form directive.
The ngSubmit
–
The ngSubmit directive specifies a function to run when the form is submitted.
Here on form submit onSubmitEmployee component method will be called.
The NgForm
-
It is nestable alias of form directive. The main purpose of ngForm is to group
the controls, but not a replacement of <form> tag.
As you know, the HTML
does not allow nesting of form elements. It is very useful to nest forms.
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