move(fromOffsets:toOffset:)

Declaration

mutating func move(fromOffsets source: IndexSet, toOffset destination: Int)

Parameters

• source:

  An index set representing the offsets of all elements that should be moved.

• destination:

  The offset of the element before which to insert the moved elements. destination must be in the closed range 0...count.

Discussion

Pass an offset as destination to indicate where in the collection the moved elements should be inserted. Of the elements that are not represented by the offsets in source, those before destination are moved toward the beginning of the collection to make room for the moved elements, while those at or after destination are moved toward the end.

In this example, demonstrating moving several elements to different destination offsets, lowercaseOffsets represents the offsets of the lowercase elements in letters:

var letters = Array("ABcDefgHIJKlmNO")
let lowercaseOffsets = IndexSet(...)
letters.move(fromOffsets: lowercaseOffsets, toOffset: 2)
// String(letters) == "ABcefglmDHIJKNO"

// Reset the `letters` array.
letters = Array("ABcDefgHIJKlmNO")
letters.move(fromOffsets: lowercaseOffsets, toOffset: 15)
// String(letters) == "ABDHIJKNOcefglm"

If source represents a single element, calling this method with its own offset, or the offset of the following element, as destination has no effect.

letters = Array("ABcDefgHIJKlmNO")
letters.move(fromOffsets: IndexSet(integer: 2), toOffset: 2)
// String(letters) == "ABcDefgHIJKlmNO"