Been talking to Marcus Boerger, via email, about the PHP 5 Standard Library article and need to confess ;)
Marcus makes a very good point about the DirectoryReader example I used;
Your DirectoryReader is wrong. It does the non file skipping in valid, but it should be done in next().
But after the necessary changes it still has a major design flaw. It uses recursion. And Iterators are about unfolding.
So what you should do is preventing that recursion and if you look at the result and how much it took you to complete it correctly you see why using FilterIterator would have been better. That one can be used to filter out the non files easily and it makes clear why iterators can be used for functional programming – in this scenario the filter algorithm provided by FilterIterator doesn’t know anything about your data.
Here’s the problem class plus code using it;
class DirectoryReader extends DirectoryIterator {
function __construct($path) {
parent::__construct($path);
}
function current() {
return parent::getFileName();
}
function valid() {
if ( parent::valid() ) {
if ( !parent::isFile() ) {
parent::next();
return $this->valid();
}
return TRUE;
}
return FALSE;
}
function rewind() {
parent::rewind();
}
}
// Create a directory reader for the current directory
$Reader = new DirectoryReader('./');
// Loop through the files in the directory ?!?
foreach ( $Reader as $Item ) {
echo $Item.'
';
}
Anyone want to take up the guantlet and re-implement?
As I understand what Marcus is saying, the alternative is to use DirectoryIterator itself then pass it to something extending FilterIterator (or perhaps better extending DirectoryFilterDots) – the “spec” is for something to list only the files in a given directory, ignoring the parent and current nodes.
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I’d go for the shortest method
class FileFilterIterator extends FilterIterator { function accept() { return $this->current()->isFile(); } } $Reader = new FileFilterIterator(new DirectoryIterator('./')); // Loop through the files in the directory ?!? foreach ( $Reader as $Item ) { echo $Item.'';
As a side note, been wondering why an abstract OuterIterator class wasn’t created in spl.
abstract class OuterIterator implements Iterator { protected $iterator; function __construct(Iterator $iterator) { $this->iterator = $iterator; } function getInnerIterator() { return $this->iterator; } function valid() { return $this->iterator->valid(); } function key() { return $this->iterator->key(); } function current() { return $this->iterator->current(); } function next() { return $this->iterator->next(); } function rewind() { return $this->iterator->rewind(); } }which then iterators like FilterIterator would have been subclasses of.
September 21st, 2004 at 9:44 pm
Re the original title – to keep life simple have changed it; not interested in the discussion that surrounds it and this is the shortest path this time.
Cant guarantee Ill do the same in future – to me, as a European, there was nothing offensive about the title – didnt even occur to me. If I start thinking about every possible culture I might offend, nothing would get written.
Thats an interesting question – guess we’d need Marcuss input on that. Talking to him and studying the design I’m very sure he had clear ideas in building the SPL iterators; the problem is I doubt he’s going to get time to explain all the decisions that influenced the design, which would help alot.
Perhaps you could propose it to him, with a use case?
September 22nd, 2004 at 6:50 am
Thanks Harry, keep up the PHP stuff, I’ve learned a LOT from you! :-)
September 22nd, 2004 at 9:04 am
I too, would like to thank you, Harry. Keep up the great work. I’ve learned a lot from you as well, including your books. (a *damn* lot) ;) ;)
September 23rd, 2004 at 1:22 am
Love your postings Harry! thanks, great job
September 23rd, 2004 at 10:08 am
Ren – message from Marcus which I think was meant to endup here;
September 25th, 2004 at 4:52 am
Ah yes, I didnt intend for getInnerIterator to be public.
I’m finding the general class helpful thou, especially when mapping either key() or current() return values to something else.
September 29th, 2004 at 6:24 pm
How about that?:)
//set_time_limit(10); class DirectoryReader extends FilterIterator { protected $iter; function __construct($path) { $this->iter = new RecursiveIteratorIterator ( new RecursiveDirectoryIterator($path) ); parent::__construct( $this->iter ); } function accept() { return $this->iter->getSubIterator()->isFile(); } } $path = dirname(__FILE__); foreach(new DirectoryReader($path) as $file) { echo $file->getPath(), ' --> ', $file->getFilename(), "\n"; /* or invoke __toString()... echo $file, "\n"; */ }October 2nd, 2004 at 1:41 pm