/**
* constructor
*
* @param \Traversable $iterator iterator to map values of
* @param callable $valueMapper optional callable which maps the values
* @param callable $keyMapper optional callable which maps the keys
* @throws \InvalidArgumentException in case both $valueMapper and $keyMapper are null
*/
public function __construct(\Traversable $iterator, callable $valueMapper = null, callable $keyMapper = null)
{
if (null === $valueMapper && null === $keyMapper) {
throw new \InvalidArgumentException('Passed null for both valueMapper and keyMapper, but at ' . 'least one of both must not be null');
}
parent::__construct($iterator);
if (null !== $valueMapper) {
$this->valueMapper = ensureCallable($valueMapper);
$this->description[] = 'values mapped by ' . describeCallable($valueMapper);
}
if (null !== $keyMapper) {
$this->keyMapper = ensureCallable($keyMapper);
$this->description[] = 'keys mapped by ' . describeCallable($keyMapper);
}
}
/**
* returns description of this iterator
*
* @return string
*/
public function description() : string
{
return 'starting at ' . $this->seed . ' continued by ' . describeCallable($this->operation);
}
public function __construct(\Iterator $iterator, callable $callback)
{
parent::__construct($iterator, ensureCallable($callback));
$this->description = describeCallable($callback);
}