angular rxjs: handle multiple http requests

Question

I have following pseudocode

objects = [obj1, obj2, obj3]    
for obj in objects {
user: http.get(obj1.user_id)
product: http.get(obj1.product_id)
}.subscribe(results => {

do something with results

})

What I want here is that, I loop through an array of objects and for each object get related user and product and then subscribe to do something with the user and product. How can I do that?

Answer 1

You could use RxJS forkJoin along with Array#map to trigger multiple observables in parallel.

const objects = [obj1, obj2, obj3];

forkJoin(
  objects.map(obj =>           // <-- `Array#map` function
    forkJoin({
      user: http.get(obj.user_id)
      product: http.get(obj.product_id)
    })
  )
).subscribe({
  next: (res) => {
    console.log(res);
    // use `res`
  },
  error: (err) => {}
});


/*
output in subscription: 
[
  { 
    user: result from `http.get(obj1.user_id)`,
    product: result from `http.get(obj1.product_id)`,
  },
  { 
    user: result from `http.get(obj2.user_id)`,
    product: result from `http.get(obj2.product_id)`,
  },
  { 
    user: result from `http.get(obj3.user_id)`,
    product: result from `http.get(obj3.product_id)`,
  }
]
*/