Instance Method

formIndex(_:offsetBy:)

Offsets the given index by the specified distance.

Declaration

func formIndex(_ i: inout Int, offsetBy distance: Int)

Parameters

i

A valid index of the collection.

distance

The distance to offset i. distance must not be negative unless the collection conforms to the BidirectionalCollection protocol.

Discussion

The value passed as distance must not offset i beyond the bounds of the collection.

Complexity: O(1) if the collection conforms to RandomAccessCollection; otherwise, O(k), where k is the absolute value of distance.

See Also

Manipulating Indices

var startIndex: Int

The position of the first element in a nonempty array.

var endIndex: Int

The array’s “past the end” position—that is, the position one greater than the last valid subscript argument.

func index(after: Int) -> Int

Returns the position immediately after the given index.

func formIndex(after: inout Int)

Replaces the given index with its successor.

func index(before: Int) -> Int

Returns the position immediately before the given index.

func formIndex(before: inout Int)

Replaces the given index with its predecessor.

func index(Int, offsetBy: Int) -> Int

Returns an index that is the specified distance from the given index.

func index(Int, offsetBy: Int, limitedBy: Int) -> Int?

Returns an index that is the specified distance from the given index, unless that distance is beyond a given limiting index.

func formIndex(inout Int, offsetBy: Int, limitedBy: Int) -> Bool

Offsets the given index by the specified distance, or so that it equals the given limiting index.

func distance(from: Int, to: Int) -> Int

Returns the distance between two indices.

var indices: Range<Int>

The indices that are valid for subscripting the collection, in ascending order.