contains(where:)

Declaration

func contains(where predicate: (Self.Element) async throws -> Bool) async rethrows -> Bool

Parameters

• predicate:

  A closure that takes an element of the asynchronous sequence as its argument and returns a Boolean value that indicates whether the passed element represents a match.

Return Value

true if the sequence contains an element that satisfies predicate; otherwise, false.

Discussion

You can use the predicate to check for an element of a type that doesn’t conform to the Equatable protocol, or to find an element that satisfies a general condition.

In this example, an asynchronous sequence called Counter produces Int values from 1 to 10. The contains(where:) method checks to see whether the sequence produces a value divisible by 3:

let containsDivisibleByThree = await Counter(howHigh: 10)
    .contains { $0 % 3 == 0 }
print(containsDivisibleByThree)
// Prints "true"

The predicate executes each time the asynchronous sequence produces an element, until either the predicate finds a match or the sequence ends.