Dealing with Angular 2's Http Map and Subscribe Problem

Looking to parse a JSON file and create a settingsProvider.

This is how I am attempting it:

import {Http} from "angular2/http";
import {Injectable} from "angular2/core";

@Injectable()
export class SettingsProvider{
    url: string = "";
    constructor(http: Http){
        http.request('js/app/config/config.json').map(data => data.json()).subscribe(data => this.url = data.url);
    }

    getUrl():string {
        return this.url;
    }

}

Encountering an error like this:

https://i.stack.imgur.com/bOSN7.png

So, my initial question is - why is this happening?

Second question:

When I try the following approach:

http.request('js/app/config/config.json').subscribe(data => {
            this.url = data.json().url;
        });

this doesn't refer to the class but to the Subscriber instance. Why does this occur? I believed that using fat-arrow lambda in TypeScript should prevent such strange closures.

Answer №1

To successfully utilize the Map function, make sure to import it from RXJS. An example of how you can do this is by including the following line:

 import 'rxjs/add/operator/map';

It's recommended not to perform HTTP requests within the constructor. Instead, create a separate method for it. Here's an updated version of the code with some modifications:

@Injectable()
export class SettingsProvider{

  constructor(public http: Http) {
  }

  getSettings() {
    // place your http request code here
  }
}

If you encounter any difficulties or need further assistance, feel free to ask for additional code snippets. Importing should resolve any issues related to the map function.

Answer №2

After encountering an error while trying to retrieve branch json data, I made a modification in my code. Instead of the previous method, I utilized $.parseJSON(res._body), and it resolved the issue successfully.

To fetch the branches, I created a function called getBranch(). This function makes use of this.http.get("/branch").map() to handle the response by using $.parseJSON(res._body). The retrieved data is then assigned to the variable 'branches'. In case of any errors, an alert message will be displayed saying 'No data found'.

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