Introduction:
If you’re working with Angular 4 and using the AsyncPipe to display data from Firebase, you may encounter the frustrating “InvalidPipeArgument: ‘[object Object] ’ for pipe ‘AsyncPipe'” error. Don’t worry; we’ve got you covered! In this article, we’ll walk you through the steps to resolve this issue and get your data displayed seamlessly. So let’s dive in.
Understanding the Error
Subheading: What Causes the ‘InvalidPipeArgument’ Error?
The ‘InvalidPipeArgument’ error occurs when you’re trying to use the AsyncPipe in Angular 4 but encounter an issue with the data being passed to it. Specifically, the error message ‘[object Object] ’ indicates that the data you’re trying to display is not in the expected format.
Identifying the Problem
Subheading: Reviewing the Code
To solve the issue, let’s first examine the code you’ve provided. We’ll analyze the service, component, and Pug template to identify any potential sources of the error.
Subheading: The MoviesService
In your MoviesService, you’ve used AngularFireDatabase to retrieve data from Firebase. The get() method returns an Observable that you’re subscribing to in your component.
Subheading: The MoviesComponent
In the MoviesComponent, you’re subscribing to the Observable returned by get(). Inside the subscription, you’re assigning each movie snap to the ‘movies’ array. However, this approach will overwrite the ‘movies’ array with each iteration, resulting in only the last movie being displayed.
Subheading: The Pug Template
In the Pug template, you’re using the AsyncPipe to display the movie titles. However, since the ‘movies’ array is overwritten in each iteration, the AsyncPipe encounters an invalid argument when trying to display the titles.
Resolving the Error
Subheading: Restructuring the Code
To fix the ‘InvalidPipeArgument’ error, we need to make some adjustments to your code. Let’s update the MoviesComponent to ensure that all movies are correctly displayed.
Subheading: Updated MoviesComponent
Replace your existing MoviesComponent code with the following:
typescriptCopy code
import { Component, OnInit } from '@angular/core';
import { MoviesService } from './movies.service';
@Component({
selector: 'app-movies',
templateUrl: './movies.component.html',
styleUrls: ['./movies.component.css']
})
export class MoviesComponent implements OnInit {
movies: any[]
;
constructor(private moviesDb: MoviesService) { }
ngOnInit() {
this.moviesDb.get().subscribe((snaps) => {
this.movies = snaps.map(snap => snap.payload.val());
});
}
}
Explanation of the Updated Code
Subheading: Retrieving All Movies
In the updated code, we use the map() function on the ‘snaps’ array to extract the values of each movie. By doing this, we obtain an array of movie objects instead of an array of snapshots. This ensures that the ‘movies’ array contains all the movies retrieved from Firebase.
Verifying the Solution
Subheading: Testing the Updated Code
Save the changes and test your application. You should now see all the movie titles displayed correctly without encountering the ‘InvalidPipeArgument’ error.
Conclusion:
Resolved the ‘InvalidPipeArgument’ error in Angular 4 when using the AsyncPipe to display data from Firebase. By restructuring your code and ensuring that all movie objects are stored in the ‘movies’ array, you can now showcase your data seamlessly. Remember to apply the updated code to any similar scenarios where you encounter a similar error.