Keeping an index with flatMap in Swift

Question

This is a follow-up to this question:

flatMap and `Ambiguous reference to member` error

There I am using the following code to convert an array of Records to an array of Persons:

let records = // load file from bundle
let persons = records.flatMap(Person.init)

Since this conversion can take some time for big files, I would like to monitor an index to feed into a progress indicator.

Is this possible with this flatMap construction? One possibility I thought of would be to send a notification in the init function, but I am thinking counting the records is also possible from within flatMap ?

Answer 1

Yup! Use enumerated().

let records = // load file from bundle
let persons = records.enumerated().flatMap { index, record in
    print(index)
    return Person(record)
}