In Angular, the decorator @ViewChild() is used to access a child component, directive, or DOM element within the parent component.
In certain cases, you may need to access a directive, child component, or DOM element from a parent component class. The ViewChild decorator returns the first element that matches the selector for a given directive, component, or template reference.
Use ViewChild with Child Component
ViewChild makes it possible to access a child component and call methods or access instance variables that are available to the child.
Let’s start, First we will create a ParentComponent and ChildComponent. Ideally, i will use @angular/cli to generate your component:
A. Generate Parent Component named “employee”
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ng g c employee |
B. Generate Child Component named “salary”
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ng g c salary |
Open and Edit salary.component.ts file
Now, I will add salaryIncrement and salaryDecrement method to ChildComponent which returns a message:
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import { Component, OnInit } from '@angular/core'; @Component({ selector: 'app-salary', templateUrl: './salary.component.html', styleUrls: ['./salary.component.css'] }) export class SalaryComponent implements OnInit { empsalary:number=0; message:string=''; constructor() { } salaryIncrement(){ this.empsalary=this.empsalary+500; this.message="Employee Incremented Salary: "; } salaryDecrement(){ this.empsalary=this.empsalary-500; this.message="Employee Decremented Salary: " } ngOnInit(): void { } } |
Next, I will edit the salary.component.html file and copy and paste the below code:
Open and Edit salary.component.html file
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<h4>{{message}} {{empsalary}}</h4> |
Next, I will open the parent component “employee.component.html” and update reference of child component selector to the parent component html file:
Open and Edit employee.component.html file
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<h4>Employee Parent Component</h4> <button (click)="increment()">Increment Salary</button> <p> </p> <button (click)="decrement()">Decrement Salary</button> <p> </p> <app-salary></app-salary> |
In the above code, i added two button for increment and decrement the salary.
Also i added the child component reference using <app-salary></app-salary> in parent template.
Open and Edit employee.component.ts file
Next, i will open the “employee.component.ts” file and define the function for button click.
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import { Component, OnInit, ViewChild } from '@angular/core'; @Component({ selector: 'app-employee', templateUrl: './employee.component.html', styleUrls: ['./employee.component.css'] }) export class EmployeeComponent implements OnInit { constructor() { } increment(){ console.log("Salary Incremented"); } decrement(){ console.log("Salary Decremented"); } ngOnInit(): void { } } |
In the above code, i only defined increment and decrement function which will trigger on button click and console the message.
Now, I will use ViewChild decorator in “employee.component.ts” file and use the increment and decrement function or method of child component “salary”.
Open and Edit employee.component.ts file again
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import { Component, OnInit, ViewChild } from '@angular/core'; import { SalaryComponent } from '../salary/salary.component'; @Component({ selector: 'app-employee', templateUrl: './employee.component.html', styleUrls: ['./employee.component.css'] }) export class EmployeeComponent implements OnInit { @ViewChild(SalaryComponent) salaryComponent:SalaryComponent; constructor() { } increment(){ this.salaryComponent.salaryIncrement(); } decrement(){ this.salaryComponent.salaryDecrement(); } ngOnInit(): void { } } |
Now, we can call the salaryIncrement and salaryDecrement method from within our parent component class with ViewChild like this:
Next, we will reference the employee component in our app template:
Open and edit app.component.html file
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<app-employee></app-employee> |
When I run the application and view the output in a browser, I get the following output
Output:
After click on increment button for first time, I get the following output.
After click on decrement button for first time , I get the following output.
Conclusion
You have learned to use ViewChild decorator to access a child component from a parent component class.
Hope I was able to help someone out. If you have any questions feel free to ask anything on the comment section. Cheers!!.
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