Re: Best way of iterating over object member fields?

On 03/09/14 18:52, David Harkness wrote:

On Wed, Sep 3, 2014 at 3:19 AM, Peter Ford <pete@justcroft.com> wrote:

RTFM works nicely :) Of course, the line gains a bit of weight: foreach (array_keys(get_class_vars('MyObject')) as $key) but at least it clears the hint.

Keep in mind that hints are just that: hints that perhaps you may simplify the code or improve performance by removing an operation that produces a value that's never used. Iterating over the keys and values of an object is an O(n) operation. Building an array of key/value mappings from an object's properties is an O(n) operation. And building another array holding just the keys (as values) is yet another O(n) operation. Thus, to remove a squiggly line under the $value variable in your IDE, you've turned an O(n) operation into an O(3n) operation. Granted, O(3n) is still O(n), but clearly it will take roughly three times as long.* And consider what happens when transforming the object to an array of key/values to an array of keys. Note that the values are accessed, packaged up into an array, and then tossed away. That's no different from ignoring the value in the loop. Moving from performance to simplicity of design, I find this form more complicated. You must recognize (or look up) the two functions to see what's happening. But the simpler loop over the object with an underlined $value is immediately obvious: you're looping over the object's properties and ignoring the values. I would revert to your original form and possibly file a feature request to support using $ without a name to indicate a throwaway variable that should not receive a value (similar to _ in Python, though I believe that is an actual variable and _ is used as a convention to indicate "I don't care about this value").

     foreach ($object as $key => $)

This would come in handy in other cases where you want to ignore values:

     list($, $author, $name) = explode(',', '123,Charles Lutwidge

Dodgson,Alice in Wonderland'); Cheers, David * Of course, array_keys and get_class_vars are internal functions and will execute faster than iteration over the resulting array or object in PHP code.

You speak a lot of sense, David - I'm leaning toward reverting the code. The IDE I'm using (NetBeans) can be tuned to turn various hints on and off, but the 'unused variable' hint that my code throws up is not fine-grained enough to handle cases where the unused variable is actually the most efficient way to do it. While your dummy variable suggestion sounds OK in principle, I'm not sure the PHP people would implement that any time soon. There are other ways to do this (another response suggests quite a nice one), but it might be better to raise an RFE on the IDE, rather than the language... -- Peter Ford phone: 01580 893333 fax: 01580 893399 Justcroft International Ltd. www.justcroft.com Justcroft House, High Street, Staplehurst, Kent TN12 0AH United Kingdom Registered in England and Wales: 2297906 Registered office: Stag Gates House, 63/64 The Avenue, Southampton SO17 1XS