Angular 2 Http Post发送两个ajax调用而不是一个

import 'rxjs/Rx';
import {Injectable,EventEmitter} from 'angular2/core';
import {Http,Response,RequestOptions,Headers,URLSearchParams} from 'angular2/http';
import {Observable} from 'rxjs/Observable'
import {GuidService} from './guid.service';

@Injectable()
export class HttpService {
    private http: Http;
    private guidService: GuidService;
    public ajaxStarted: EventEmitter<string> = new EventEmitter();
    public ajaxCompleted: EventEmitter<string> = new EventEmitter(); 

    constructor(http: Http,guidService: GuidService) {
        this.http = http;
        this.guidService = guidService;
    }

    public post(url: string,model: any): Observable<Response> {
        let headers = new Headers({ 'Content-Type': 'application/json' });
        let options = new RequestOptions({ headers: headers });

        //Create unique id for each ajax call
        let httpCallId = this.guidService.new();

        //Let Loading Box components that an ajax call has been triggered
        this.ajaxStarted.emit(httpCallId);

        let httpPost = this.http.post(url,JSON.stringify(model),options);

        //Let Loadinc Box Component know that ajax call has been completed
        httpPost.subscribe(success => this.ajaxCompleted.emit(httpCallId),error => this.ajaxCompleted.emit(httpCallId));

        return httpPost;
    }

}

这是我在代码提交时调用的代码：

@Component({
    selector: 'register',templateUrl: './app/account/components/register.view.html',directives: [ROUTER_DIRECTIVES]
})
export class RegisterComponent {
    private accountDataService: AccountDataService

    public registerViewModel: AccountViewModel.UserRegistrationViewModel;

    constructor(accountDataService: AccountDataService) {
        this.accountDataService = accountDataService;
        this.registerViewModel = <AccountViewModel.UserRegistrationViewModel>{};
    }

    public register() {
        this.accountDataService.register(this.registerViewModel).subscribe(x => {
            console.log(x);
        })
    }
}     

<form (ngSubmit)="register()" #userRegistrationForm="ngForm">
            <div class="form-group">
                <input class="form-control" 
                       type="email" 
                       placeholder="Email Address"
                       [(ngModel)]="registerViewModel.userName" />
            </div>
            <div class="form-group">
                <input class="form-control" 
                       type="password" 
                       placeholder="Password"
                       [(ngModel)]="registerViewModel.password" />
            </div>
            <div class="form-group">
                <input class="form-control" 
                       type="password" 
                       placeholder="Password Confirmation"
                       [(ngModel)]="registerViewModel.confirmPassword" />
            </div>
            <div class="form-group">
                <button type="submit" 
                        class="btn btn-fluid btn-primary"
                        [disabled]="!userRegistrationForm.form.valid">Register</button>
            </div>
        </form>

现在我的问题是当我点击提交按钮而不是一个ajax调用来发送到服务器.我已经通过在服务器上放置一个制动点并且两个呼叫到达来检查这一点.

只有在点击按钮时才会调用注册函数.

我注意到我的问题是这一行：

httpPost.subscribe(success => this.ajaxCompleted.emit(httpCallId),error => this.ajaxCompleted.emit(httpCallId));

如果我评论它只有一个ajax调用被发送到服务器.

我理解observables的方式是,当可观察值发生变化时,每个订阅都会被触发.

我在这做错了什么？

更新：

该问题显然也在get调用中复制.我的应用程序中的所有get调用都调用了函数：

public get(url: string,model: any = {}): Observable<Response> {
    let httpCallId = this.guidService.new();

    this.ajaxStarted.emit(httpCallId);

    let httpGet = this.http.get(url,new RequestOptions({
        headers: this.getHttpHeaders(),search: this.createURLSearchParams(model)
    }));

    httpGet.subscribe(success => this.ajaxCompleted.emit(httpCallId),error => this.ajaxCompleted.emit(httpCallId));

    return httpGet;
}