init(_:)

Creates an iterator that wraps a base iterator but whose type depends only on the base iterator’s element type.

Declaration

init<I>(_ base: I) where Element == I.Element, I : IteratorProtocol

Parameters

base:
An iterator to type-erase.

Discussion

You can use AnyIterator to hide the type signature of a more complex iterator. For example, the digits() function in the following example creates an iterator over a collection that lazily maps the elements of a Range<Int> instance to strings. Instead of returning an iterator with a type that encapsulates the implementation of the collection, the digits() function first wraps the iterator in an AnyIterator instance.

func digits() -> AnyIterator<String> {
    let lazyStrings = (0..<10).lazy.map { String($0) }
    let iterator:
        LazyMapSequence<Range<Int>, String>.Iterator
        = lazyStrings.makeIterator()

    return AnyIterator(iterator)
}