Using multiple flatMap responses within the map operator across various functions: a guide

Question

Using multiple flatMap responses within the map operator across various functions: a guide

I've been working on a solution to connect multiple operations within a map function that follows the flatMap operator.

Here's how it currently functions:

flatMap(
  someResponse => combineLatest([
    this.locator.function(someResponse, variable2),
    this.function1(someResponse),
  ])
),
map(([response1, response2]) => this.function3(response1, response2));

The new functionality I aim for is as follows:

flatMap(someResponse =>
  combineLatest([
    this.locator.function(someResponse, variable2),
    this.function1(someResponse),
    this.locator.function2(someResponse, variable3)
  ])
),
map(([response1, response2, response3]) => {
  this.function3(response1, response2);
  this.function4(response3);
})

I attempted using another map, but it retrieved the previous map response instead of the flatMap. My understanding of each of these operators like switchMap, concatMap, mergeMap, etc., isn't entirely solid. Hence, I couldn't figure out a way to achieve this.

In the flatMap, I've linked and merged three functions, and now I wish to utilize the responses for additional operations.

Can someone guide me on accomplishing this task?

angular typescript rxjs

Answer 1

Answer №1

There could be alternative solutions, however for now the provided solution should suffice.

In the first case, you are returning the array resulting from

this.function3(response1, response2)

. This is because arrow functions without curly braces essentially translate to a function with a return statement. For example, map((...) => function(...)) is equivalent to

map((...) => { return function(...)) }

.

Therefore, in the second scenario, create an object and insert the arrays returned by both functions into it. Finally, return the object.

flatMap(someResponse =>
  combineLatest([
    this.locator.function(someResponse, variable2),
    this.function1(someResponse),
    this.locator.function2(someResponse, variable3)
  ])
),
map(([response1, response2, response3]) => {
  return {
    'result1': this.function3(response1, response2),
    'result2': this.function4(response3)
  }
})

After subscribing to the observable, the arrays generated from functions 1 and 2 can be accessed through response.result1 and response.result2 respectively.

Answer 2

There could be alternative solutions, however for now the provided solution should suffice.

In the first case, you are returning the array resulting from

this.function3(response1, response2)

. This is because arrow functions without curly braces essentially translate to a function with a return statement. For example, map((...) => function(...)) is equivalent to

map((...) => { return function(...)) }

.

Therefore, in the second scenario, create an object and insert the arrays returned by both functions into it. Finally, return the object.

flatMap(someResponse =>
  combineLatest([
    this.locator.function(someResponse, variable2),
    this.function1(someResponse),
    this.locator.function2(someResponse, variable3)
  ])
),
map(([response1, response2, response3]) => {
  return {
    'result1': this.function3(response1, response2),
    'result2': this.function4(response3)
  }
})

After subscribing to the observable, the arrays generated from functions 1 and 2 can be accessed through response.result1 and response.result2 respectively.

Using multiple flatMap responses within the map operator across various functions: a guide

Answer №1

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