Using an object as a parameter vs creating the object in the method

Question

During a discussion, I wasn't sure if I was correct when saying:

"It's better to pass around objects as parameters instead of object ID's."

So I thought I'd ask here for clarification.

What are the advantages of doing this:

public function doSomething(\Item $item) 
{   
     return $item->getSomething() * 2;
}

Over this:

public function doSomething($itemID) 
{
    $item = \Item::getByID($itemID); // Return an item based on ID
    if ($item) // Check the object has been returned
    {
       return $item->getSomething() * 2;
    }
}

Is it true to say that one benefit is you can presume the object will exist, so there is no need to check if it does?

Mark Baker · Accepted Answer · 2014-03-21 14:58:11Z

4

It's called dependency injection, and the main benefit is that you can test the doSomething() method in complete isolation by injecting a "mock" Item object into the method, so testing doSomething() isn't dependent on the logic of Item itself

answered Mar 21, 2014 at 14:58

Mark Baker

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2 Comments

paul Over a year ago

Ah of course. Are there any other benefits unrelated to testability?

Mark Baker Over a year ago

Other benefits, like you can pass object of class Item or of classes that extend class Item; whereas your second version forces you to instantiate an object of type Item unless you jump through some hoops in the getByID() method - that gives you additional flexibility.... that's the L of SOLID

Michael Bartel · Accepted Answer · 2014-03-21 15:02:19Z

0

The first solution may be a little bit faster at runtime. You should prefer that to the second inside of a loop. The second does a look up for the item by its ID.

answered Mar 21, 2014 at 15:02

Michael Bartel

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