Introduction:
Angular is a popular open-source platform for building web applications. It offers many features to make the development process easier and quicker. One such feature is @input. The @input decorator in Angular is used to create a property that can be set or passed from a parent component to a child component.
In this article, we will discuss the use of @input in Angular and its various properties. We will also answer some Frequently Asked Questions (FAQs) related to this topic.
@Input decorator:
The @Input decorator in Angular is used to create a property that can be set or passed from a parent component to a child component. This is useful when you want to communicate between different components in your application.
The @Input decorator can be added to any property of a child component class. It takes an optional parameter that is the name of the input property. If the parameter is not provided, then the property name is used.
Here is an example of how to create an input property using @Input decorator:
“`
import { Component, Input } from ‘@angular/core’;
@Component({
selector: ‘child-component’,
template: `
The value of myInput is {{ myInput }}
`
})
export class ChildComponent {
@Input() myInput: string;
}
“`
In this example, we import the Input decorator from the @angular/core module and use it to decorate the myInput property. We then use this property in the template of the child component to display its value.
Properties of @Input:
The @Input decorator has a few properties that can be used to customize its behavior. Here are some of the properties that are frequently used:
1. @Input() propertyName: string;
This is the basic usage of @Input, where you simply provide the property name and the input is created.
2. @Input(‘alias’) propertyName: string;
You can give an alias to the input property by specifying it in the decorator. This is useful when you want to change the name of the input property for clarity.
“`
import { Component, Input } from ‘@angular/core’;
@Component({
selector: ‘child-component’,
template: `
The value of myInputAlias is {{ myInputAlias }}
`
})
export class ChildComponent {
@Input(‘myInputAlias’) myInput: string;
}
“`
In this example, the input property is created with the alias myInputAlias.
3. @Input() set propertyName(value: any)
You can use a setter function to process the value of the input property. This is useful when you want to perform some action whenever the input property changes.
“`
import { Component, Input } from ‘@angular/core’;
@Component({
selector: ‘child-component’,
template: `
The value of myInput is {{ myInput }}
`
})
export class ChildComponent {
private _myInput: string;
@Input()
set myInput(value: string) {
this._myInput = value.toUpperCase();
}
get myInput() {
return this._myInput;
}
}
“`
In this example, we use a setter function to convert the input value to uppercase and store it in a private variable. Whenever the input value changes, the setter function is called and the new value is processed.
FAQs:
Q. What is the difference between @Input and @Output in Angular?
A. @Input is used to pass data from a parent component to a child component, while @Output is used to emit an event from a child component to a parent component.
Q. Can I pass an object as an @Input property?
A. Yes, you can pass an object as an input property. However, you need to be careful about the object’s reference. If the object reference changes, then the child component will not receive the updated object.
Q. Can I have multiple @Input properties in a child component?
A. Yes, you can have multiple @Input properties in a child component. You can decorate each of them with @Input and provide a unique name for each property.
Q. Can I pass a function as an @Input property?
A. No, you cannot pass a function as an input property. However, you can create a method in the child component that accepts a function as an argument and calls it whenever required.
Conclusion:
The @Input decorator in Angular is a useful feature that allows you to pass data from a parent component to a child component. It has many properties that can be used to customize its behavior. In this article, we discussed the various properties of @Input and answered some frequently asked questions related to this topic.