Returns an index that is the specified distance from the given index.
Required. Default implementation provided.
SDK
- Xcode 10.0+
Framework
- Swift Standard Library
Declaration
func index(_ i: Self.Index, offsetBy distance: Int) -> Self.Index
Parameters
iA valid index of the collection.
distanceThe distance to offset
i.distancemust not be negative unless the collection conforms to theBidirectionalprotocol.Collection
Return Value
An index offset by distance from the index i. If distance is positive, this is the same value as the result of distance calls to index(after:). If distance is negative, this is the same value as the result of abs(distance) calls to index(before:).
Discussion
The following example obtains an index advanced four positions from a string’s starting index and then prints the character at that position.
let s = "Swift"
let i = s.index(s.startIndex, offsetBy: 4)
print(s[i])
// Prints "t"
The value passed as distance must not offset i beyond the bounds of the collection.
Complexity: O(1) if the collection conforms to Random; otherwise, O(k), where k is the absolute value of distance.