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Angular2 Http Request

Hi I am trying to make a get request using the HTTP module in Angular2.

Everything compiles fine in Typescript (1.5), but Chrome shows the following error the in console:

EXCEPTION: Error during instantiation of EntryList!. ORIGINAL
EXCEPTION: TypeError: Cannot read property 'merge' of undefined
ORIGINAL STACKTRACE: TypeError: Cannot read property 'merge' of undefined
at mergeOptions (angular2.dev.js:27991)  
at execute.Http.get (angular2.dev.js:28052)  
at EntryService.getEntries (services.js:17)
at new EntryList (entry-list.js:20)

Services.ts

/// <reference path="../typings/angular2/angular2.d.ts" />
import { Http, Observable } from "angular2/angular2"

export class EntryService {
    private _entries: Array<string>;
    private _http : Http;

    constructor() {     
        this._entries = ["test1", "test2", "test3"];
        this._http = new Http;      
    }

    get Entries() : Array<string> {
        return this._entries;
    }

    getEntries()
    {
        console.log(this._http);
        return this._http.get('http://localhost:53338/api/decisions')       
            .toRx()
            .map((response) => { 
                response.json()
            });     
    }
}

entry-list.ts

/// <reference path="../typings/angular2/angular2.d.ts" />
/// <reference path="../modules/services.ts" />

import { Component, View, NgFor } from "angular2/angular2"
import { EntryService } from "modules/services"

@Component({
    selector: 'entry-list'  
})
@View({
    directives: [ NgFor ],
    templateUrl: "../views/entry-list.html" 
})
export class EntryList {
    entries: Array<string>; 

    constructor(public service: EntryService) {     
        this.entries = this.service.Entries;
        this.service.getEntries().subscribe((response) => {     
            console.log(response);
        }); 
    }
}

app.ts

/// <reference path="typings/angular2/angular2.d.ts" />
/// <reference path="components/entry-list.ts" />
/// <reference path="modules/services.ts" />

import { Component, View, bootstrap, NgFor } from "angular2/angular2"
import { EntryList } from "components/entry-list"
import { EntryService } from "modules/services"

@Component({
    selector : "app",
    bindings: [ EntryService ]  
})
@View({
    directives: [ EntryList ],
    templateUrl: "views/app.html"   
})
class App { 
    constructor() {
        console.log('hit');
    }
}

bootstrap(App);

index.html

<html>
    <head>
        <title>SCM</title>
        <script src="https://github.jspm.io/jmcriffey/[email protected]/traceur-runtime.js"></script>
        <script src="https://jspm.io/[email protected]"></script>      
        <script src="https://code.angularjs.org/2.0.0-alpha.34/angular2.dev.js"></script>
    </head>
    <body>
        <app></app>
        <script>System.import('app')</script>
    </body>
</html> 

I did look at the API documentation on the angular.io site, but can't see whats wrong.

UPDATE

Services.ts

/// <reference path="../typings/angular2/angular2.d.ts" />
import { Http, Observable, httpInjectables } from "angular2/angular2"

export class EntryService {
    private _entries: Array<string>;    

    constructor(private http: Http) {       
        this._entries = ["test1", "test2", "test3"];            
    }

    get Entries() : Array<string> {
        return this._entries;
    }

    getEntries()
    {
        console.log(this.http);
        return this.http.get('http://localhost:53338/api/decisions')        
            .toRx()
            .map((response) => { 
                response.json()
            });     
    }
}

entry-list.ts

/// <reference path="../typings/angular2/angular2.d.ts" />
/// <reference path="../modules/services.ts" />

import { Component, View, NgFor, Http, httpInjectables } from "angular2/angular2"
import { EntryService } from "modules/services"

@Component({
    selector: 'entry-list',
    bindings : [ Http, httpInjectables ]
})
@View({
    directives: [ NgFor ],
    templateUrl: "../views/entry-list.html" 
})
export class EntryList {
    entries: Array<string>; 

    constructor(public service: EntryService) {     
        this.entries = this.service.Entries;
        this.service.getEntries().subscribe((response) => {     
            console.log(response);
        }); 
    }
}

app.ts

/// <reference path="typings/angular2/angular2.d.ts" />
/// <reference path="components/entry-list.ts" />
/// <reference path="modules/services.ts" />

import { Component, View, bootstrap, NgFor, Http, httpInjectables } from "angular2/angular2"
import { EntryList } from "components/entry-list"
import { EntryService } from "modules/services"

@Component({
    selector : "app",
    bindings: [ EntryService, Http, httpInjectables ]   
})
@View({
    directives: [ EntryList ],
    templateUrl: "views/app.html"   
})
class App { 
    constructor() {
        console.log('hit');
    }
}

bootstrap(App);

Without any changes into index.html

Edit: My services.ts file changes to get this working:

/// <reference path="../typings/angular2/angular2.d.ts" />
import { Injector, Http, httpInjectables } from "angular2/angular2"

export class EntryService {
    private _entries: Array<string>;    
    private http: Http;

    constructor() {     
        this._entries = ["test1", "test2", "test3"];        

        var injector = Injector.resolveAndCreate([
                httpInjectables,
                Http
            ]);
        this.http = injector.get(Http);                 
    }

    get Entries() : Array<string> {
        return this._entries;
    }

    getEntries()
    {       
        return this.http.get('http://localhost:53338/api/decisions')        
            .toRx()
            .map(response => response.json());      
    }
}
like image 972
Werner Swart Avatar asked Aug 19 '15 13:08

Werner Swart


Video Answer


1 Answers

You should not instantiate Http yourself, instead get it injected :

public constructor(http : Http) {
    this.http = http;
}

The documentation says :

Http is available as an injectable class, with methods to perform http requests.

Therefore I am not sure what is the result if you instantiate it yourself, but somehow it can't manage to do the get request due to some internals that are undefined.

Edit: Adding more sources.

@Injectable()
export class Http {
    constructor(protected _backend: ConnectionBackend, protected _defaultOptions: RequestOptions) {}

    /**
     * Performs a request with `get` http method.
     */
    get(url: string, options?: RequestOptionsArgs): EventEmitter {
        return httpRequest(this._backend, new Request(mergeOptions(this._defaultOptions, options, RequestMethods.GET, url)));
  }
}

Here I added a little part of the Http class from the github repo. You can see that _backend and _defaultOptions are given in the constructor which you don't give, and the method get() will build options for the request based on the options parameter and the _defaultOptions given in the constructor, since you provide none of these, I believe it crashes in the mergeOptions call that you can find here :

function mergeOptions(defaultOpts, providedOpts, method, url): RequestOptions {
  var newOptions = defaultOpts;
  if (isPresent(providedOpts)) {
    // Hack so Dart can used named parameters
    newOptions = newOptions.merge(new RequestOptions({
      method: providedOpts.method,
      url: providedOpts.url,
      search: providedOpts.search,
      headers: providedOpts.headers,
      body: providedOpts.body,
      mode: providedOpts.mode,
      credentials: providedOpts.credentials,
      cache: providedOpts.cache
    }));
  }
  if (isPresent(method)) {
    return newOptions.merge(new RequestOptions({method: method, url: url}));
  } else {
    return newOptions.merge(new RequestOptions({url: url}));
  }
}

At the last if/else of the function. For more information the source file is located here.

like image 59
Arnaud Boeglin Avatar answered Oct 10 '22 11:10

Arnaud Boeglin