Instance Property インスタンスプロパティ

indices

The indices that are valid for subscripting the collection, in ascending order. コレクションの添え字に使うのに有効である、昇順でのインデックス。

Declaration 宣言

var indices: Value.Indices { get }

Available when Value conforms to MutableCollection.

Discussion 議論

A collection’s indices property can hold a strong reference to the collection itself, causing the collection to be nonuniquely referenced. If you mutate the collection while iterating over its indices, a strong reference can result in an unexpected copy of the collection. To avoid the unexpected copy, use the index(after:) method starting with startIndex to produce indices instead.

var c = MyFancyCollection([10, 20, 30, 40, 50])
var i = c.startIndex
while i != c.endIndex {
    c[i] /= 5
    i = c.index(after: i)
}
// c == MyFancyCollection([2, 4, 6, 8, 10])