[SOLVED] Object Interfaces

[Daniel0]

What is the purpose of object interfaces? I don't really see why you would want to set which methods a class must implement. Why would/should people use them?

[Jenk]

interface DoesSomething
{
    public function doSomething ();
}

class Foo
{
    public function bar (DoesSomething $obj)
    {
        $obj->doSomething();
    }
}

 

It assures that $obj conforms to the interface of DoesSomething; if it didn't - it may not have the method doSomething() which could have catastophic results compared to the light-weight error received for not implementing the interface.

[obsidian]

Interfaces are an extremely useful tool when you have multiple people working on a project and you want to make sure that everyone is adhering to the same coding goals and procedure. This is only one example of a valid usage for them, but a pretty solid one nonetheless. If I can provide you with an interface that X number of classes you write must follow, I can go ahead and start writing the supporting pages knowing exactly how they will interact with your code once it's handed over.

[Daniel0]

So it is just to ensure that other people (and yourself) will adhere to however you want the class to be and not really anything else?

[utexas_pjm]

So it is just to ensure that other people (and yourself) will adhere to however you want the class to be and not really anything else?

 

Here is a somewhat practical example using interfaces:  You can see that the following code would be impossible in strongly typed languages (i.e., Java) and impractical in loosely types languages (PHP):

 

<?php
interface DataEntityFactory
{
public function buildEntity($row);
}

class DogEntityFactory implements DataEntityFactory
{
public function buildEntity($row)
{
	$dog = new Dog();

	$dog->setId($row['id']);
	$dog->setName($row['name']);

	return $dog;
}
}

class CatEntityFactory implements DataEntityFactory
{
public function buildEntity($row)
{
	$cat = new Cat();

	$cat->setId($row['id']);
	$cat->setName($row['name']);

	return $cat;
}
}

class DataMapper
{
function mapData($rs, $factory)
{
	$entities = array();

	foreach($rs as $row){
		$entities[] = $factory->buildEntitiy($row);
	}

	return $entities;
}
}

$dogs = DataMapper::mapData(DBAbstractionClass(GET_ALL_DOGS_SQL), new DogEntittyFactory());
$cats = DataMapper::mapData(DBAbstractionClass(GET_ALL_CATS_SQL), new CatEntittyFactory());

?>

 

[Daniel0]

Ok. Thanks everybody