http.get(..).map function is not working with alpha 48 #5632

@Injectable()
export class WPService implements IWPService {
    baseURL: string = 'http://localhost/wptest/api';
    http: Http;
    constructor(http: Http) {
        this.http = http;
    }
    GetPosts() {
        var query = this.baseURL + '/get_posts/';
        return new JsonObject(this.http.get(query));
    }
}

@Injectable()
export class JsonObject {
    constructor(json: Observable<any>) {
        json.map(res => res.json()).map(data => {          // <= 
            for (var entry in data) {
                if (data.hasOwnProperty(entry)) {
                    this[entry] = data[entry];
                }
            }
        }).subscribe();
    }
}