Return Value 戻り値
A sequence of the initial, consecutive elements that satisfy predicate.
Instance Method
インスタンスメソッド
prefix(while:)
Returns a sequence containing the initial, consecutive elements that satisfy the given predicate.
Availability 有効性
- iOS 13.0+
- iPadOS 13.0+
- macOS 10.15+
- Mac Catalyst 13.0+
- tvOS 13.0+
- watchOS 6.0+
Technology
- Swift
UI
Declaration 宣言
func prefix(while predicate: (Self.Element) throws -> Bool) rethrows -> [Self.Element]Parameters パラメータ
predicateA closure that takes an element of the sequence as its argument and returns a Boolean value indicating whether the element should be included in the result.
Discussion 議論
The following example uses the prefix(while:) method to find the positive numbers at the beginning of the numbers array. Every element of numbers up to, but not including, the first negative value is included in the result.
let numbers = [3, 7, 4, -2, 9, -6, 10, 1]
let positivePrefix = numbers.prefix(while: { $0 > 0 })
// positivePrefix == [3, 7, 4]If predicate matches every element in the sequence, the resulting sequence contains every element of the sequence.