PHP extending a class

Question

I have a question about extending a class in PHP.

The examples I see on the php site just have 1 line of code in the method...is it the same if the method has tons of code??

If this is the base class:

class BaseClass {

    public function WithWayTooMuchCode {
      // like 100 lines of code here
    }

}

Then do I have to copy all the code over if I want to use the same method, but change only 1 or 2 things?

class MyOwnClass extends BaseClass {
     public function WithWayTooMuchCode {
      // like 100 lines of code here

     // do I have to copy all of the other code and then add my code??
    }

}

This seems a little not DRY to me...

Yes you have to do this, but you could write a workaround and split up the big function into seperate functions and only overwrite those. — Johannes Klauß
– Johannes Klauß, Commented May 11, 2012 at 15:18
Indeed. With modular OO design this won't be a (very nasty) problem. — TaZ
– TaZ, Commented May 11, 2012 at 15:19
Sure, but this does not solve the problem. Because what if he wants to overwrite an internal algorithm that does some math on a returned variable? parent::methodName() does not help in this case. — Johannes Klauß
– Johannes Klauß, Commented May 11, 2012 at 15:35

mpen · Accepted Answer · 2012-05-11 15:20:30Z

5

Yes, unless those 1 or 2 things happen to be at the beginning or the end. You can call the parent function via

parent::WithWayTooMuchCode();

Which you can place anywhere in the child/overridden method.

If it doesn't feel DRY, consider splitting the function into smaller methods.

answered May 11, 2012 at 15:20

mpen

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2 Comments

redconservatory Over a year ago

By that, do you mean split the BaseClass into smaller methods or MyOwnClass into smaller methods? Either way could you possibly point me to a code example (I have been looking but without luck). Thanks so much!

mpen Over a year ago

@redconservatory: Neither. You want to split WithWayTooMuchCode into smaller methods; if the bulk of the code is in the version that's in the base class, then add the helper methods to the base too. If you don't need them in the base, put them in the derived class. The idea to put them as "close" as possible to where you need them. You might also consider making them private if you don't need them to be publicly accessible. I can't point you to examples... all you're doing is breaking a big function into smaller functions.

Kristian · Accepted Answer · 2012-05-11 20:23:55Z

4

do I have to copy all the code over if I want to use the same method, but change only 1 or 2 things?

No, you don't have to copy all of the code, assuming you're adding to the function and not removing pieces of it.

so it follows:

class BaseClass {

    public function WithWayTooMuchCode {
      // like 100 lines of code here
    }

}

class MyOwnClass extends BaseClass {

    public function WithWayTooMuchCode { 
        parent::WithWayTooMuchCode();
        //additionally, do something else
    }

}

$moc = new MyOwnClass();
$moc->WithWayTooMuchCode();

edited May 11, 2012 at 20:23

answered May 11, 2012 at 15:20

Kristian

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Comments

Userbn · Accepted Answer · 2012-05-11 15:24:50Z

2

You can use the parent::WithWayTooMuchCode() wich will execute the parent method and after you can add your code. It will look like this :

class MyOwnClass extends BaseClass {
     public function WithWayTooMuchCode {
      parent::WithWayTooMuchCode()

     // do I have to copy all of the other code and then add my code??
    }

}

answered May 11, 2012 at 15:24

Userbn

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Comments

Rajan Rawal · Accepted Answer · 2012-05-11 15:25:44Z

1

You can write down a separate function for that things that you want to do separately in parent class and then Call then in you way.

In other words, separate out the things you need to do separately ans create a function for them. And call them separately in child class. The final function in child class will call parent class function as well those separate functions.

answered May 11, 2012 at 15:25

Rajan Rawal

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Comments

Laurence · Accepted Answer · 2012-05-11 15:27:47Z

You have a few choices. Assuming;

class BaseClass {

    public function WithWayTooMuchCode {
      // like 100 lines of code here
       }
    }

You can do

class MyOwnClass extends BaseClass {
     public function AnotherFunction() {
         // put other code here
    }

}

This allows you to do MyOwnClass->AnotherFunction() and MyOwnClass->WithWayTooMuchCode()

or you could do

class MyOwnClass extends BaseClass {
     public function WithWayTooMuchCode() {
         // put new code here
    }

}

which will allow you to run MyOwnClass->WithWayTooMuchCode() and will ONLY run the "new code", not the "100 lines".

Finally you could do

class MyOwnClass extends BaseClass {
     public function WithWayTooMuchCode() {
         parent::WithWayTooMuchCode();
         // Do more processing
    }

}

which will allow you to run MyOwnClass->WithWayTooMuchCode() will run the "100 lines of code" AND the new code. You can put the parent before/after/during your new code, so you can tailor it as required

Manos Dilaverakis · Accepted Answer · 2012-05-11 15:30:50Z

0

In addition to the other answers I should point out that this problem can be addressed by events. They are a way to determine points in a class where you can add your own functionality from outside. If you have control over the codebase and the time/inclination you might want to consider implementing this functionality. Unfortunately PHP doesn't support them directly in the way that, say, C# does so you'd have to do the work.

If you only have this issue in a single place I doubt you should bother, but if it's becoming a pattern you might want to consider this approach.

answered May 11, 2012 at 15:30

Manos Dilaverakis

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