On Aug 2, 2005, at 9:05 AM, Derick Rethans wrote:
Problems:
1. There is no way to document the 'virtual' properties with any of
the existing
documentation tools (such as phpdoc and doxygen)
This sounds like a tool problem, not a language problem.
2. There is no way how the magic methods know if a specific 'virtual'
property
exists or not as those properties are not declared usually - unless
you
define an array with property names as a class constant (which is
not
allowed either).
Sometimes you just want to know if a single property exists and
sometimes you want to know all the properties. There are cases where
generating the full list of properties may be overly expensive (ORM
with inheritance).
__has_property($name)
__get_property_list()
Note that some properties may be read only and some might be write
only, so perhaps incorporating intended use into the API:
__has_readable_property($name)
__has_writable_property($name)
__get_readable_properties()
__get_writable_properties();
3. There is no way for the magic methods to return a meaningfull error
when a
property doesn't "exist". Of course it is possible to throw an
error with
"trigger_error" or "throw" in case a property doesn't "exist" in a
specific
class, but the file and line numbers would not match the actually
get/set
action. debug_backtrace() can be used to retrieve the correct file
and line,
but as you have to do this for every class where you want to use
setters and
getters *and* you have to implement your own error message rendering
function this is not really a suitable option either.
I would rather see exceptions used instead of changing the established
method signature of __get and __set. What about defining a standard
PropertyNotFound exception?
While on the topic, a little wishlisting. i would like to see an
accessor method search path, much like Objective C's KeyValueCoding:
http://developer.apple.com/documentation/Cocoa/Conceptual/
KeyValueCoding/index.html
so, this defines a read only virtual property:
class Square {
function __get_area() {
return $this->width*$this->length;
}
}
echo $sq->area;
in this case, PHP would look for a __get_XXX method before calling the
__get as a last resort fallback. I'm not attached to this particular
syntax, but I think the KVC concept with an accessor method naming
convention has proven worthwhile in Objective C. KVC also has some
interesting advanced features such as indexed properties, paths, change
notification, and constraint enforcement. KVC is worth emulating.
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