AngularFire2: Perform 'Joins' on FirebaseListObservables using RxJS .map()

Question

As stated in another question, I\'m developing an Ionic 2 App using Firebase as Backend.

I have categories and I have products. Products belong to categories. As it

Answer 1

I solved the problem.

provider (*.ts):

getProductsOfCategory(catId){
  let result = this.af.database.list('/categories/'+catId+'/prods')
    .map(items => { 
      for (let product of items) { 
        this.af.database.object('/products/'+product.$key)
        .subscribe( data => {
          product.details = data;
        });
      }
      return items;        
    })      
  return result;
}


getCategoriesAndProducts(){
  let result = this.af.database.list('/categories')
    .map(items => { 
      for (let category of items) {
        this.getProductsOfCategory(category.$key)
        .subscribe(data => {
          category.productDetails = data;
        })
      }
      return items;
    })
  return result;
}

provider call in the tempaltes ts-file:

getCategoriesAndProducts(){
    this.categoryService.getCategoriesAndProducts()
      .subscribe(data => {
          this.categoriesAndProducts = data;
});

template / view (*.html):

  
    

      {{cat.cat_name}}
    
    
      
                    
          
            {{subcat.cat_name}}
          
          
            {{prod.details?.prod_name}}