Instance Method

first(where:)

Returns the first element of the sequence that satisfies the given predicate.

Declaration

func first(where predicate: (Entity) throws -> Bool) rethrows -> Entity?

Parameters

predicate

A closure that takes an element of the sequence as its argument and returns a Boolean value indicating 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

The following example uses the first(where:) method to find the first negative number in an array of integers:

let numbers = [3, 7, 4, -2, 9, -6, 10, 1]
if let firstNegative = numbers.first(where: { $0 < 0 }) {
    print("The first negative number is \(firstNegative).")
}
// Prints "The first negative number is -2."

Complexity: O(n), where n is the length of the sequence.

See Also

Finding Entities

func contains(Entity) -> Bool

Returns a Boolean value indicating whether the sequence contains the given element.

func contains(where: (Entity) -> Bool) -> Bool

Returns a Boolean value indicating whether the sequence contains an element that satisfies the given predicate.

func allSatisfy((Entity) -> Bool) -> Bool

Returns a Boolean value indicating whether every element of a sequence satisfies a given predicate.

var first: Entity?

The first element of the collection.

func max(by: (Entity, Entity) -> Bool) -> Entity?

Returns the maximum element in the sequence, using the given predicate as the comparison between elements.

func min(by: (Entity, Entity) -> Bool) -> Entity?

Returns the minimum element in the sequence, using the given predicate as the comparison between elements.

func randomElement() -> Entity?

Returns a random element of the collection.

func randomElement<T>(using: inout T) -> Entity?

Returns a random element of the collection, using the given generator as a source for randomness.