Access class properties directly, vs. via methods

[bunner_bob]

Say I have a class:

class Foo
{
    var $bar;

function ShowBar($value)
{
    $this->bar = $value;
    echo $this->bar;
}
}

Normally I would run this with:

$foo = &new Foo;
$foo->ShowBar('waffle');

or some such.

But, I could also leave out the $value parameter in ShowBar(), and say:

$foo = &new Foo;
$foo->bar = 'waffle';
$foo->ShowBar();

Obviously in this case the latter method is more complicated, but in cases where there are a number of class properties that may or may not need setting, it's hard to write class methods that handle this varying number of parameters. It becomes much easier to set properties 'directly' - or leave them null, and have the class behave accordingly.

So what's wrong with doing it this way? I gather it's not a good idea, but why I don't know.

• Bob

[bunner_bob]

...and by "properties" I actually mean "attributes" 🙂

In further reading, I see the reason has more to do with following accepted standards (as related to public and private attributes) than whether it will work (it does, in PHP4 anyway).

I also see that a popular way to access attributes from outside is to write set and get methods for each attribute you might want to access.

So you have:

function setBar($value)
{
$this->bar = $value;
}

function getBar()
{
return $this->bar;
}

The drag of this is having to write a separate function (or pair of functions) for every attribute you might want to access from outside.

Any favorite ways of getting around this? Such as...

function setAttribute($attribute_name, $value)
{
$this->$attribute_name = $value;
}

function getAttribute($attribute_name)
{
return $this->$attribute_name;
}

is this wise? Seems terribly clever, but we know how THAT always turns out...

[Weedpacket]

The subject has come up before (one thread I know of is http://www.phpbuilder.com/board/showthread.php?s=&threadid=10272276); the point of accessor methods is that it insulates the user of the class from its internal workings: just because a class has getFoo() and setFoo() methods that work exactly as you'd expect doesn't mean that there has to be a $foo property inside.

Your generic (get|set)Attribute method allows users to set (and attempt to get) any property they like - whether it exists or not.