first(where:)
Returns the first element of the sequence that satisfies the given predicate.
Declaration
func first(where predicate: (Self.Element) async throws -> Bool) async rethrows -> Self.Element?Parameters
- predicate:
A closure that takes an element of the asynchronous sequence as its argument and returns a Boolean value that indicates whether the element is a match.
Return Value
The first element of the sequence that satisfies predicate, or nil if there is no element that satisfies predicate.
Discussion
In this example, an asynchronous sequence called Counter produces Int values from 1 to 10. The first(where:) method returns the first member of the sequence that’s evenly divisible by both 2 and 3.
let divisibleBy2And3 = await Counter(howHigh: 10)
.first { $0 % 2 == 0 && $0 % 3 == 0 }
print(divisibleBy2And3 ?? "none")
// Prints "6"The predicate executes each time the asynchronous sequence produces an element, until either the predicate finds a match or the sequence ends.