Retrieving information from a JSON file utilizing an Interface

For the purpose of learning, I am developing a small Ionic app where I want to load data from a JSON file and map it to an interface that defines the data structure. However, I am facing challenges in achieving this:

import { Component } from "@angular/core"; 
import { HttpClient} from "@angular/common/http";

export interface PhonebookEntry {
    name:           string,
    telephone:      string, 
    description:    string
}

@Component({
    selector:    'page-phonebook',
    templateUrl: 'phonebook.html'
})
export class PhonebookPage {

    entries: Array<PhonebookEntry>;

    constructor(public http: HttpClient) {
        this.load_entries('assets/json/phonebook.json');
    };

    load_entries(filePath: string) {
        return this.http.get(filePath)
            .subscribe(
                data => this.entries = data
            );
    };

}

It seems like only the line data => this.entries = data is causing an issue (my IDE is indicating that), but I am unsure of the correct way to handle this. I have searched for documentation on this topic without success. If anyone knows of any resources that can help, I would greatly appreciate it.

Answer №1

When subscribing, the response is returned as an object rather than an array, so the type of entries needs to be adjusted.

entries: PhonebookEntry;

To properly handle the response data in the subscribe method, a type should be assigned.

load_entries(filePath: string) {
    return this.http.get(filePath)
        .subscribe(
            (data: PhonebookEntry) => this.entries = data // or use any type
        );
};

Check out the demo here!

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