Sharing functions across unrelated classes

Question

I'm still working my head around object orientated programming and getting away from procedural programming. Although I use classes I know I still don't write my code fully OOP. I've been reading and doing my best to get as much information and practice as I can to further my abilities and I'm making progress, but one area that I'm currently confused on is how to deal with an independent function that would be reused across multiple classes that are entirely unrelated.

I understand I can extend classes, or implement an interface, or use a trait. I found this post, which was very helpful in clarifying things, however I'm still confused what is the correct method to use in this situation. For example, I have a function that will generate a random alphanumeric string to a length specified by an input, and will return that string. Several classes, not related, can use this function and it makes no sense to include the function in each class.

To me the most obvious thing is a library of common functions in a trait, which I can then just use in a class as needed. However is this the proper way to do things?

score 2 · Accepted Answer · answered Feb 16 '13 at 23:13

2

Yes, absolutely.

You don't need traits for utilities, just make a library. If you want to be tidy and stick to the object-oriented paradigm, create utility classes that group several static methods performing similar tasks - instead of creating large PHP files containing a bunch of functions that pollute the global scope.

answered Feb 16 '13 at 23:13

gd1

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Would you just then extend that class when you need to include the functions or would you assign the class to a variable and include the variable as a global? – Styphon Feb 16 '13 at 23:18
I would also add that the classes with static methods should probably be `abstract`. These tend to pair well with `static` methods. since they do not need to be called on a specific instance of a class, but can be called in general. – Adam_G Feb 16 '13 at 23:19
@Styphon: please read the PHP documentation about the meaning of the keyword `static`, example #2. You don't need to extend the utility class, instantiate it or whatever. :) – gd1 Feb 16 '13 at 23:28
@Adam_G I guess making them abstract is just a way for preventing them to be instantiated. According to me, it's not necessary and can be confusing... – gd1 Feb 16 '13 at 23:28
@gd1 - Ah, gotcha. This seems like the most logical way to manage them to me. Thank you. – Styphon Feb 16 '13 at 23:34

score 0 · Answer 2 · edited May 23 '17 at 12:08

For example, I have a function that will generate a random alphanumeric string to a length specified by an input, and will return that string. Several classes, not related, can use this function and it makes no sense to include the function in each class.

It's not a function. It's a responsibility. A good rule of thumb is to forget functions exist when doing OOP. Your function is a class RandomAlphanumericStringGenerator. It has one method generate that accepts $length as an input, which will generate and return the string. Create an instance of that Generator and inject it to objects that have need for this.

Sharing functions across unrelated classes

2 Answers2