Instance Method

first(where:)

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

Declaration

func first(where predicate: (UInt8) throws -> Bool) rethrows -> UInt8?

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 Bytes

func max() -> UInt8?

Returns the maximum element in the sequence.

func max(by: (UInt8, UInt8) -> Bool) -> UInt8?

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

func min() -> UInt8?

Returns the minimum element in the sequence.

func min(by: (UInt8, UInt8) -> Bool) -> UInt8?

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

func range(of: Data, options: Data.SearchOptions, in: Range<Data.Index>?) -> Range<Data.Index>?

Finds the range of the specified data as a subsequence of this data, if it exists.

typealias Data.SearchOptions

Options that control a data search operation.

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