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

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:
        LazyMapIterator<IndexingIterator<Range<Int>>, String>
        = lazyStrings.makeIterator()

    return AnyIterator(iterator)
}

• Parameter base: An iterator to type-erase.

Declaration

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

Creates an iterator that wraps the given closure in its next() method.

The following example creates an iterator that counts up from the initial value of an integer x to 15:

var x = 7
let iterator: AnyIterator<Int> = AnyIterator {
    defer { x += 1 }
    return x < 15 ? x : nil
}
let a = Array(iterator)
// a == [7, 8, 9, 10, 11, 12, 13, 14]

• Parameter body: A closure that returns an optional element. body is executed each time the next() method is called on the resulting iterator.

Declaration

@inlinable public init(_ body: @escaping () -> Element?)

Advances to the next element and returns it, or nil if no next element exists.

Once nil has been returned, all subsequent calls return nil.

Declaration

@inlinable public func next() -> Element?