Understanding Data Sharing with @Input() in Angular

In Angular, parent and child components often need to communicate with each other. This can be achieved through different methods, and one of the most common ways is by using the @Input() decorator. According to the quiz question, passing data from the parent component to the child component in Angular is correctly performed by using the @Input() function.

The @Input() decorator in Angular is part of the @angular/core module, which allows data to be passed from a parent component into a child component. By placing @Input() before a property in the child component, you are essentially opening a doorway to accept data from the parent component.

For instance, we might have a simple parent component like this:

import { Component } from '@angular/core';

@Component({
  selector: 'app-parent',
  template: `<app-child [childData]="parentData"></app-child>`
})
export class ParentComponent {
  parentData = "Hello from Parent Component!"
}

And a corresponding child component:

import { Component, Input } from '@angular/core';

@Component({
  selector: 'app-child',
  template: `<p>{{childData}}</p>`
})
export class ChildComponent {
  @Input() childData: string;
}

In the example above, we are using the @Input() decorator to bind the 'childData' property in the child component to receive data ('parentData') from its parent component.

On the other hand, using @Output() is incorrect for this scenario because @Output() is designed for the opposite case - it allows the child component to emit events to the parent component, not to receive data.

The 'Input' and 'Output' without the '@' symbol are also incorrect because in Angular, they don’t carry any special significance and would just be treated as standard properties.

The best practice when using @Input() in Angular is to declare it within the child component where the value is required. It is also considered a good practice to keep track of changes to the Input property by using the OnChanges lifecycle hook in the child component.

The @Input() thus acts as an effective and recommended method to pass data from parent component to child component in Angular, ensuring seamless data sharing and boosting the robustness of Angular applications.