CODEWITHSUNDEEP
phpooptraits
Cameron Ball
Cameron Ball

Reputation: 4108

When is it appropriate to use a trait in PHP?

I've been reading up about PHP's traits. Specifically I came across this article. They probide an example involving objects that need to implement a shareable interface. The following argument is presented:

Does it make sense to duplicate the share() method in every class that implements the Shareable interface?

No.

Does it make sense to have an AbstractShare class that objects who implement the Shareable interface extend?

No.

Does it make sense to have the share() method implemented as part of an AbstractEntity class, but then blocked out for the Message object?

No.

Does it make sense to implement a ShareableTrait that fulfils the interface contract and can therefore be easily added to only objects that require it?

Yes!

I can understand the first and third points. But the second one confuses me. What exactly is wrong with having an abstract class called AbstractShareable or something like that which contains the functionality to share something, and then extending from it?

Upvotes: 4

Views: 522

Answers (1)

deceze
deceze

Reputation: 522076

An interface is specifically designed to create reliable, well, interfaces, independent of the implementing class. Meaning:

function (Shareable $sharable) {
    $shareable->share();
}

You can be assured that this code will always work (any object being passed in having a share() method), due to your interface declaration.

You can achieve the same thing using a class hierarchy; i.e. if you require a certain class, you can be sure that all of its children will also have the same methods the parent has. But: this imposes a strict class hierarchy on your classes. All classes have to extend one specific base class. And they can only extend that one specific class. You couldn't use a class hierarchy for both an AbstractSharable and an AbstractLoggable, say. That's why the class hierarchy solution is too inflexible. It would only allow you to implement one "trait". Or you'd have to mash all your various "traits" together into the same base class. Then you have a giant monolithic base class.

Separating characteristics into small individual interfaces keeps your code simple and flexible. Traits provide a flexible implementation analogue to an interface's specification.

Upvotes: 1

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