Re: [fw-db] find() returns rowset

All excellent points Bill, I couldn't agree more. Great work.

-Sam

On Wed, Aug 20, 2008 at 2:36 PM, Bill Karwin <bill@karwin.com> wrote:

ah125i wrote:
>
> I was under the impression we have Zend_Db_Table_Rowset because it

> implements SeekableIterator and Countable
>

Yes.  The Rowset class has some other object methods on it, like toArray().
It's also serializable, so you can put a Rowset in a cache.

The find() method may result in zero, one, or more rows.  When I joined the
ZF team, this method  returned either a Row or Rowset object, but I changed
it.  It seemed confusing that a method may return two different types,
depending on its arguments.  Also, what should it return if the search
matches zero rows in the database?  Null?  So now I would have to test the
return value for three possible types?  (null/Row/Rowset)

$result = $table->find( ...args ... );
if ($result === null) {
 // zero rows matched
} elsif ($results instanceof Zend_Db_Table_Row) {
 // one row matched
} elsif ($results instanceof Zend_Db_Table_Rowset) {
 if (count($results) == 0) {
   // zero rows matched
 } else {
   // multiple rows matched
 }
}

Note that some overlap cases exist.  You can give two values (123, 456), so
you're asking for multiple rows.  But suppose only a row matching 123
exists, no row matching 456.  Should find() return a Rowset or a Row?  Does
the return type depend on what you ask for, or what the result is?

I felt the best way to make it "simple" was always to return a Rowset.  That
handles all three cases of zero rows, one row, or several rows.  The Rowset
has an interface for testing if it's empty, getting the first row, or
iterating over multiple rows.  But the point is that you know what that
interface is, without having to branch on the object's type.

If it's a little awkward to call $rowset->current() to get the first row,
surely it's much more awkward to write a big if/elsif/else structure to test
the result type every time you call find().

Regards,
Bill Karwin
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--
Sam Sandberg

"Well, everyone knows Custer died at Little Bighorn. What this book presupposes is... maybe he didn't?"
-Eli Cash