[英]How to fetch data from firestore and inside it fetch another data (by reference)
I can't figure out how to fetch data from firestore when i have in data model reference (id) to another object, for example like this 当我在数据模型引用(id)中引用另一个对象时,例如我这样,我不知道如何从firestore中获取数据
City {name: string;
countryId: string; //primary key to another object in database
}
Country {
name: string;
}
I m using AngularFire 5. 我正在使用AngularFire 5。
After i fetch city i want fetch country and i want to asign country.name to city.countryId and i want return joined object city. 在我获取城市之后,我想要获取国家,并且我想要将country.name分配给city.countryId,并且我希望返回加入的对象城市。
I made service for this because i want fetch this data from multiple places in code. 我为此提供了服务,因为我想从代码的多个位置获取此数据。
@Injectable()
export class CityService implements OnInit {
city: City;
constructor(
private dataFetch: FireStoreService) { }
ngOnInit() {}
getCity(ref: string): City {
this.dataFetch.getDataDoc(ref).subscribe((_city: City) => {
this.dataFetch.getDataDoc(_city.countryId)
.subscribe((country: Country) => {
_city.countryId = country.name;
this.city = _city;
});
});
return this.city;
}
}
Ye i know this will not work beacause it is async task, i have read a lot of articles, but i can not still figure out. 是的,我知道这是行不通的,因为它是异步任务,我已经阅读了很多文章,但是我仍然无法弄清楚。 So I don't know how to fetch some object and then fetch references from this object and return joined object (without references but with proper data).
因此,我不知道如何获取某个对象,然后从该对象获取引用并返回联接的对象(没有引用但有适当的数据)。
This is my city component. 这是我的城市组成部分。
@Component({
selector: 'app-detail-city',
template: `
<p> detail-city works! </p>
<p> Name : {{ city.name }} </p>
<p> Country : {{ city.countryId }} </p>
<p> ID : {{ city.id }} </p>
`,
styleUrls: ['./detail-city.component.css']
})
export class DetailCityComponent implements OnInit {
city: City;
root: string;
constructor(
private route: ActivatedRoute,
private cityService: CityService) {
this.route.params.subscribe(
(params: Params) => {
this.root = params['root']+'/'+params['id'];
this.city = cityService.getCity(this.root);
});
}
ngOnInit() {}
}
So i manage to solve this problem at the end. 因此,我最终解决了这个问题。 Here is code from servis.
这是来自Servis的代码。
getCity(ref: string): Observable<City> {
return this.dataFetch.getDocument(ref)
.switchMap((res: City) => {
return this.dataFetch.getDocument(res.countryId)
.map((country: Country) => {
return new City(
res.id,
res.name,
country.name
);
});
});
}
Then you can subscribe to this observable in your component or use async pipe. 然后,您可以在组件中订阅此可观察项,也可以使用异步管道。 Also, I found usefull link where is described how to use reference and geo type in FireStore.
此外,我发现了有用的链接 ,其中描述了如何在FireStore中使用参考和地理类型。
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