On Fri, Jun 6, 2008 at 2:09 PM, Tyson Vanover <tvanover@xxxxxxx> wrote:
> Sorry, I probably should have included the add() function from the parent.
> As well as all of the parent constructor.
>
> Basically the object takes an array of key=>value pairs and parses them
> into a string for output. When it takes in the array of pairs it needs to
> check the keys against a list of valid keys. I have no preference on how to
> store the list of valid keys other than to add more a constructor doesn't
> need to be called.
>
> class parent{
> $validkeys = 'name,size';
> $attributes = array();
>
> __construct($set){
> foreach($set as $key=>$value){
> if(isValidKey($key)){
> $this->attributes[$key] = $value;
> }
> }
> }
>
> __toString(){
> $output = "";
> foreach($this->attributes as $key=>value){
> $output .= sprintf(TEMPLATE, $key, $value);
> }
> }
>
> __set($key, $value){
> if(isValidKey($key)){
> $this->attributes[$key] = $value;
> }
> }
>
> isValidKey($key){
> ...Something goes here...
> }
> }
>
> class child extends parent{
> ...All this needs to do is tack on values 'color,shape' to parent's valid
> keys...
> }
>
> class grandchild extends child{
> ...All this needs to do is tack on values 'cost,location' to child's valid
> keys...
> }
>
> Most sub classes won't need anything different from their parent but the
> expanded list of valid keys.
perhaps instead of subclassing you could write a set of decorators, with a
base decorator, that the others extend. something like this,
class BaseParentDecorator {
protected $additionalValidKeys = array();
protected $theParent = null;
public function __construct($parent) {
$this->theParent = $parent;
}
public function __toString() {
return $this->theParent->__toString();
}
public function __set($key, $value) {
$this->theParent->$key = $value;
}
public function isKeyValid($key) {
/// determine if key is valid, by looking at $this->validKeys
/// put that boolean result in a variable, like $isKeyValid, then
return $isKeyValid || $this->theParent->isKeyValid($key);
}
}
and now, instead of subclassing parent, to a potentially deep hierarchy, all
your new classes will subclass BaseParentDecorator, so working off your
example from above, we would have something like,
class child extends BaseParentDecorator {
protected $validKeys = array(/* tacked on values for child */);
}
class grandchild extends BaseParentDecorator {
protected $validKeys = array(/* tacked on values for grandchild */);
}
then at runtime you simply wrap a child instance by the grandchild instance,
as in
$thing = new grandchild(new child(new parent(array(/* stuff */)));
-nathan
