第一次在angular2中呈现时，更改检测在路由页面上不起作用

Question

我正在尝试从父组件获取google maps值到我为其创建了共享服务的路由组件

import {Injectable}     from 'angular2/core';
import {Subject} from "rxjs/Subject";
@Injectable()
export class SearchService {

    private addressmap= new Subject<Sharedcomponent >();

    public searchaddressStream$ = this.addressmap.asObservable();

    broadcastaddressChange(address: Sharedcomponent ) {
        this.addressmap.next(address);
    }
}
export class Sharedcomponent {
    country: string;
    state: string;
    city: string;  
    street: string;
}

从父级开始，我正在广播此地址的值更改，并通过订阅该地址将其接收到子级，并且仅当子级页面由父级呈现时，该地址才能正常工作。 如果先渲染父级，则我通过路由调用子视图，那么渲染页面时它不会在开始时显示数据，仅当我再次更改父级中的值时才会显示。 子视图正在订阅该服务，但呈现时未获取数据。 如果您需要父母或视图提供更多解释或代码，请告诉我。 希望有人可以帮助我。

更新

这是更新，因此您可以了解我的问题，这是我从Google Maps API获取值的我的应用程序组件

declare var google: any;

@Component({
    selector: 'my-app',
    templateUrl: 'app/app.component.html',
    directives: [ROUTER_DIRECTIVES, ProductComponent],
    providers: [ SearchService]
})


export class AppComponent  {

    constructor(private _http: geoService, private sharedService: SearchService, private cdr: ChangeDetectorRef) {



    }
    ngOnChanges() {
        this.sharedService.broadcastTextChange(this.street);
        this.cdr.detectChanges();
    }
    public maps: geoResult;
    public cat_error: Boolean = false;
    public xml_Latitude :any;
    public xml_Lang: any;
    public city: string;
    public state: string;
    public coutnry: string;
   public street= new SharedService;
    public input: any;
    public autocomplete: any;

    ngOnInit() {
       var instance = this,
       autocomplete;
        if (navigator.geolocation) {
            navigator.geolocation.getCurrentPosition(res=> {
                instance._http.getPlaces(res.coords.latitude, res.coords.longitude).subscribe(
                    data=> {
                        instance.maps = data;
                        console.log(instance.maps);
                        var result = instance.maps.status;
                        var result2 = instance.maps.results;
                        if (result != "undefined" || "" || null) {

                            instance.setValue(result2[0].address_components[6].long_name, result2[0].address_components[5].long_name, result2[0].address_components[4].long_name);
                        }

                    });
            });
        }
        instance.input = document.getElementById('google_places_ac');
        autocomplete = new google.maps.places.Autocomplete(instance.input, { types: ['(cities)']});
        google.maps.event.addListener(autocomplete, 'place_changed', function () {
            var place = autocomplete.getPlace(); console.log(place);
            if (place.address_components[3] != undefined ) {
                instance.setValue(place.address_components[3].long_name, place.address_components[2].long_name, place.address_components[1].long_name);
            } else
            {
                instance.setValue(place.address_components[2].long_name, place.address_components[1].long_name, place.address_components[0].long_name);
            }
        });



    }


    setValue(a, b, c) {

        this.street.country = a;
        this.street.state = b;
        this.street.city = c;
        this.sharedService.broadcastTextChange(this.street);

    }


}

后来我有一个孩子的看法，得到这个价值

  ngOnInit() {


        this.getNewProduct();
        this.getlocation();


   }
    getlocation() {
        this.shared.searchTextStream$.subscribe(
            text => {
                this.street = text;
                this.country = this.street.country;
                this.state = this.street.state;
                this.city = this.street.city
                console.log(this.country, this.state, this.city);
            }, error=> { console.log(<any>error);}
        );
    }



    getNewProduct() {

        this._productService.selectproduct(0)
            .subscribe(
            product  => {
                this.model = product;

                this.isloading = false;
            console.log(this.model)
            },
            error => this.errorMessage = <any>error);

    }

}

但是我在渲染此视图时并没有获得地理定位，如果我更改了父级文本框中的值，那么它会在视图中更新

Answer 1

如果您想收听最后一个广播，即使您尚未订阅，也需要使用BehaviorSubject而不是Subject 。 在这种情况下，即使您在广播之后订阅，也将获得最新的更新。 这是您当前的情况该代码来自Github中的 RxJS存储库

BehaviorSubject只给您最后一个值。 如果需要最后10个或2个值，请改用ReplaySubject 。

    /*
 * BehaviorSubject
 *
 * Subject that remembers the last (or initial) value
 */

var xs = new Rx.BehaviorSubject()
xs.subscribe(logAllObserver('BehaviorSubject'))
//=> BehaviorSubject - Value: undefined

var xs = new Rx.BehaviorSubject('default')
xs.subscribe(logAllObserver('BehaviorSubject'))
//=> BehaviorSubject - Value: default

var xs = new Rx.BehaviorSubject('default')
xs.onNext('new one')
xs.subscribe(logAllObserver('BehaviorSubject'))
//=> BehaviorSubject - Value: new one

Answer 2

import {Injectable,EventEmitter}     from 'angular2/core';
import {Subject} from "rxjs/Subject";
@Injectable()
export class SearchService {

   searchaddressStream$:EventEmitter<Sharedcomponent> = new EventEmitter();

    broadcastaddressChange(address: Sharedcomponent ) {
        this.searchaddressStream$.emit(address);
    }
}

---

ngOnInit() {
        this.getNewProduct();
        // this.getlocation();
}
ngViewAfterInit()
{
   this.getlocation();
}