Detect if Observable not found using combineLatest - angularjs

Question

I need to modify my code where loading detail category will first look whether it is not already loaded in the statement, and if not then detail loads. Thanks for help!
Constructor of CategoryProvider:
private _obServers = {
'categoryList': undefined,
'category': undefined,
'idCategory': new Subject<Number>()
};
constructor(){
this.categories = new Observable(observer => this._obServers.categoryList = observer).share();
this._categoryObservable = this.categories
.combineLatest(this._obServers.idCategory, (categories, idCategory) => {
return categories.filter(category => category.id === idCategory)[0];
})
.distinctUntilChanged((oldCategory, newCategory) => {
return oldCategory.id === newCategory.id;
});
}
CategoryList:
loadCategories(search?:string):void{
this._http
.get('/services/category/list?search=' + search)
.map(res => res.json())
.subscribe(data => {
this._obServers.categoryList.next(this.createCategoryEntities(data));
});
}
CategoryDetail:
loadCategory(categoryId:number){
this._obServers.idCategory.next(categoryId);
//If category not loaded I need to load it
}

Answer 1

I have followed this way https://github.com/JonatanSCS/Angular-2-Tutorial/blob/master/node_modules/rxjs/src/add/observable/combineLatest.ts
import { Component, Injectable, Inject, provide } from '#angular/core';
import { HTTP_PROVIDERS } from '#angular/http';
import { Observable } from 'rxjs/Observable';
import { combineLatestStatic } from 'rxjs/operator/combineLatest.js';
import { MessageApi } from '../providers/lb-service/lb-services.provider'
import { EstimatesService } from './estimates.service';
#Component({
pipes: [TranslatePipe],
})
#Injectable()
export class InvoiceService {
constructor(private _message:MessageApi,
#Inject(EstimatesService) _estimates:EstimatesService) {
this._message = _message;
this._estimates = _estimates;
Observable.combineLatest = combineLatestStatic;
declare module 'rxjs/Observable' {
namespace Observable {
export let combineLatest: typeof combineLatestStatic;
}
}
Observable.combineLatest(
this._estimates.getEstimates(),
this._message.findOne({
where: {
moduleTag: 'monthlyStat',
'dynamic.date': "2016-07-01" //new Date
},
fields: {
dynamic: true
}
}),this._message.findOne({
where: {
moduleTag: 'areaPriceSE1',
'dynamic.date': ''
},
fields: {
dynamic: true
}
})
).subscribe(res => console.log("observable", res));