Instance Method


Returns a subsequence, up to the specified maximum length, containing the initial elements of the collection.


func prefix(_ maxLength: Int) -> Data



The maximum number of elements to return. maxLength must be greater than or equal to zero.

Return Value

A subsequence starting at the beginning of this collection with at most maxLength elements.


If the maximum length exceeds the number of elements in the collection, the result contains all the elements in the collection.

let numbers = [1, 2, 3, 4, 5]
// Prints "[1, 2]"
// Prints "[1, 2, 3, 4, 5]"

Complexity: O(1) if the collection conforms to RandomAccessCollection; otherwise, O(k), where k is the number of elements to select from the beginning of the collection.

See Also

Selecting Bytes

func filter((UInt8) -> Bool) -> Data

Returns a new collection of the same type containing, in order, the elements of the original collection that satisfy the given predicate.

func prefix(through: Int) -> Data

Returns a subsequence from the start of the collection through the specified position.

func prefix(upTo: Int) -> Data

Returns a subsequence from the start of the collection up to, but not including, the specified position.

func prefix(while: (UInt8) -> Bool) -> Data

Returns a subsequence containing the initial elements until predicate returns false and skipping the remaining elements.

func suffix(Int) -> Data

Returns a subsequence, up to the given maximum length, containing the final elements of the collection.

func suffix(from: Int) -> Data

Returns a subsequence from the specified position to the end of the collection.