How to use Loop in PromiseKit 6? - ios

Question

I have a function called chaining which chains multiple promises and I want to call that function multiple times. For that, I am using a for loop and I want that with index 0, the chaining function should be executed with index 0. (I have an array of properties ListingArray[] and I want to use ListingArray[0] in one iteration of loop, ListingArray[1] in other iteration and so on).
Here is my chaining function:
func chaining() {
firstly {
Promise_getIDOfOwnerFromCollection()
}.then { (IdsInCollection)-> Promise<[String]> in
return self.Promise_getOwnerListings(IDs: IdsInCollection)
}.then { (ownerListings) ->Promise<Void> in
return self.Promise_getReviews(ListingIDs: ownerListings)
}.done { (arg0) in
let () = arg0
print("Work Done")
}.catch { (error) in
print("Error is \(error.localizedDescription)")
}
}
And I am calling that function in loop like this.
for Count in 0...4 {
chaining()
}
Now the problem is that the function inside firstly is instantly called 5 times before then is executed. And I want the sequence to be like with Count 0, chaining function should execute one time and then with Count 1, function should execute again.

Answer 1

The behaviour happening in your code is completely expected. Given you're instantiating the chaining 4 times, therefore the firstly job will be executed such number of times.
Instead you will need somehow provide a single instance of work for the firstly.
Currently: execute N times { firstly + rest of the job }
Expected: firstly + execute N times { rest of the job }
Here a code example based on yours.
struct Review {
}
func Promise_getReviews(listingIDs ids: [String]) -> Promise<[Review]> {
}
func Promise_getOwnerListings(IDs ids: [String]) -> Promise<[String]> {
}
func chaining(from initialWork: Promise<[String]>) {
firstly { when(fulfilled: initialWork) }
.then(Promise_getOwnerListings)
.then(Promise_getReviews)
.done { print("Work Done") }
.catch { print("Error") }
}
let initialWork = Promise<[String]>(["1","2", "3"])
(0...3).forEach { chaining(from: initialWork) }