typealias Iterator
A type that provides the sequence’s iteration interface and encapsulates its iteration state.
typealias Element
A type representing the sequence’s elements.
シーケンスのもつ要素それらを表しているある型。
nil
if no next element exists.Availability 有効性
Technology
mutating func next() -> Date
?
The next element in the underlying sequence, if a next element exists; otherwise, nil
.
Repeatedly calling this method returns, in order, all the elements of the underlying sequence. As soon as the sequence has run out of elements, all subsequent calls return nil
.
You must not call this method if any other copy of this iterator has been advanced with a call to its next()
method.
The following example shows how an iterator can be used explicitly to emulate a for
-in
loop. First, retrieve a sequence’s iterator, and then call the iterator’s next()
method until it returns nil
.
let numbers = [2, 3, 5, 7]
var numbersIterator = numbers.makeIterator()
while let num = numbersIterator.next() {
print(num)
}
// Prints "2"
// Prints "3"
// Prints "5"
// Prints "7"
typealias Iterator
typealias Element