This tutorial lesson demonstrates how to create a component @Input()
, use it to pass data to a component for customization.
Time required: expect to spend about 10 minutes to complete this lesson.
This lesson starts with the code from the previous lesson, so you can:
If you haven't reviewed the introduction, visit the Introduction to Angular tutorial to make sure you have everything you need to complete this lesson.
If you have any trouble during this lesson, you can review the completed code for this lesson, in the live example for this lesson.
HousingLocationComponent
template has a HousingLocation
property to receive input.Inputs allow components to share data. The direction of the data sharing is from parent component to child component.
To receive data from a parent component, a child component must mark a class property with the @Input()
decorator. This decorator can be used in components and directives.
For a more in depth explanation, please refer to the Sharing data between child and parent directives and components guide.
In this lesson, you'll define @Input()
properties in the HousingLocationComponent
component which will enable you to customize the data displayed in the component.
Perform these steps on the app code in your IDE.
This step imports the Input
decorator into the class.
In the code editor:
Navigate to src/app/housing-location/housing-location.component.ts
Update the file imports to include Input
and HousingLocation
:
import { Component, Input } from '@angular/core'; import { CommonModule } from '@angular/common'; import { HousingLocation } from '../housinglocation';
In the same file, add a property called housingLocation
of type HousingLocation
to the HousingLocationComponent
class. Add an !
after the property name and prefix it with the @Input()
decorator:
export class HousingLocationComponent { @Input() housingLocation!: HousingLocation; }
You have to add the !
because the input is expecting the value to be passed. In this case, there is no default value. In our example application case we know that the value will be passed in - this is by design. The exclamation point is called the non-null assertion operator and it tells the TypeScript compiler that the value of this property won't be null or undefined.
Save your changes and confirm the app does not have any errors.
Correct any errors before you continue to the next step.
In this lesson, you created a new property decorated with the @Input()
decorator. You also used the non-null assertion operator to notify the compiler that the value of the new property won't be null
or undefined
.
If you are having any trouble with this lesson, you can review the completed code for it in the live example.
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Licensed under the Creative Commons Attribution License 4.0.
https://angular.io/tutorial/first-app/first-app-lesson-05