I'm tempted to argue that you're *not* sticking to Design By Contract here,
because your two `Stream` implementations do not themselves give the same
contract... at least, the parts of the contract that you're wanting to be
derived by the IDE.
Since it's already necessary to use a `/* @var */` comment block to
typehint your local variable, and you don't want to hint specifically on
your two classes, then perhaps you can do this instead:
/* @var $stream Stream|Iterator|IteratorAggregate */
foreach ($stream as $item) {
$item->...
}
That leaves you only hinting on interfaces...
CRB
On Saturday, October 13, 2018 at 5:06:26 PM UTC-5, Alan Gabriel Bem wrote:
>
> It is easy if such interface already extends some kind of iterator...
>
> interface Stream extends IteratorAggregate
> {
> /**
> * @return Item[]
> */
> public function getIterator();
> }
>
> ...or...
>
> interface Stream extends Iterator
> {
> /**
> * @return Item
> */
> public function current();
> }
>
> ...so IDEs have no problems with inferring actual type that variable of
> type `Stream` iterates over...
>
> /* @var $stream Stream */
> foreach ($stream as $item) {
> $item->... // works, *Item* class methods are suggested
> }
>
> ...but what if we want to delay the decision of iteration mechanism?
> Like...
>
> interface Stream extends Traversable
> {}
>
> ...so later on we can do this:
>
> class InMemoryStream implements Stream, IteratorAggregate
> {
> public function __construct(Item ...$items)
> {
> $this->items = $items;
> }
>
> // rest of the code goes here
>
> /**
> * @return Item[]
> */
> public function getIterator()
> {
> return new ArrayIterator($this->items);
> }
> }
>
> class DatabaseStream implements Stream, Iterator
> {
> // rest of the code goes here
>
> public function rewind()
> {
> $this->statement = $this->connection->prepare('SELECT * FROM
> items');
> $this->statement->execute();
> $this->current = $this->statement->fetch(\PDO::FETCH_ASSOC);
> $this->key = 0;
> }
>
> public function next()
> {
> $this->current = $this->statement->fetch(\PDO::FETCH_ASSOC);
> $this->key++;
> }
>
> public function key()
> {
> return $this->key;
> }
>
> public function valid()
> {
> return false !== $this->current;
> }
>
> /**
> * @return Item
> */
> public function current()
> {
> return new Item($this->current);
> }
> }
>
> Unfortunately IDEs, as can be expected, can't handle this.
>
> /* @var $stream Stream */
> foreach ($stream as $item) {
> $item->... // not enough information for IDEs to suggest type that
> $stream iterates over.
> }
>
> AFAIK at this moment the only solution for such case is to annotate
> variables in user-land... every time.
>
> /* @var $stream Stream|A[] */
> foreach ($stream as $item) {
> $item->... // works
> }
>
> // or worse
>
> /* @var $stream DatabaseStream */
> foreach ($stream as $item) {
> $item->... // works but annotation specifies actual implementation
> which violates Design by Contract principle
> }
>
>
>
> It bugs me personally, but I would like to hear your opinion on this and
> possible solution.
>
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