map(_:)

Creates an asynchronous sequence that maps the given closure over the asynchronous sequence’s elements.

iOS: 13.0+
macOS: 10.15+
tvOS: 13.0+
watchOS: 6.0+

@preconcurrency func map<Transformed>(_ transform: @escaping (Self.Element) async -> Transformed) -> AsyncMapSequence<Self, Transformed>

Mangled symbol

sSci12_ConcurrencyE3mapyAA16AsyncMapSequenceVyxqd__Gqd__7ElementQzYaclF What are these?

FNV24 hash: 1Q1K3

Parameters

transform: A mapping closure. transform accepts an element of this sequence as its parameter and returns a transformed value of the same or of a different type.

Returns

An asynchronous sequence that contains, in order, the elements produced by the transform closure.

Use the map(_:) method to transform every element received from a base asynchronous sequence. Typically, you use this to transform from one type of element to another.

In this example, an asynchronous sequence called Counter produces Int values from 1 to 5. The closure provided to the map(_:) method takes each Int and looks up a corresponding String from a romanNumeralDict dictionary. This means the outer for await in loop iterates over String instances instead of the underlying Int values that Counter produces:

let romanNumeralDict: [Int: String] =
    [1: "I", 2: "II", 3: "III", 5: "V"]

let stream = Counter(howHigh: 5)
    .map { romanNumeralDict[$0] ?? "(unknown)" }
for await numeral in stream {
    print(numeral, terminator: " ")
}
// Prints "I II III (unknown) V "