Exception handling in angular 2

1. we need to use "catch" operator
2. Pass it to error handling method
3. The error handling method has only  one parameter the error response                                      
4. In this message we can handle errors appropriately

Note

• The observable has a do operator that allows us to peak the data returned from the server without disrupting the flow
• We also need 2 import operator one for "d"o and one for "catch"

Sample code for error handling

import {Injectable } from '@angular/core';
//used for http and response
import {Http,Response } from '@angular/http';
//used for observable
import {Observable } from 'rxjs/Observable';
//Used for map operator. This loads the operator without importing
import 'rxjs/add/operator/map'
// used for do operator
import 'rxjs/add/operator/do';
// used for catch operator
import 'rxjs/add/operator/catch';

export class ProductService{
    //we need to change it to the actual web server
    private _productUrl='api/products/products.json'
    //constructor
    constructor(private _http:Http){}
    getProducts():Observable<IProduct>[]{
        return this._http.get(this._productUrl)
                   // when we get the response we use the map operator
                        .map((response:Response)=> <IProduct[]> response.json())
                        // allows us to peak the data returned from the server without disrupting the flow
                        .do( data=> console.log('All:'+ JSON.stringify(data)))
                        .catch(this.handleError);
    }
    //method to handle error
    private handleError(error: Response) {
        console.error(error);
        return Observable.throw(error.json().error || 'Server error');

    }                  

}