验证类的设计正确吗？

Question

I'd like to create a class that will validate form input (please no comments about reinventing the wheel).

I'm thinking it makes more sense to have a class with static validation methods, rather than having to instantiate a validation object since the object wouldn't hold any data?

So for example, something like:

<?php

class Validator {

    static function is_numeric($val) {

        if(is_numeric($val))
            return true;

    }

}

Would allow me to use:

if(!Validator::is_numeric($_POST['age'])) $error['age'] = "Age must be a number";

Whereas:

<?php

class Validator {

    public function is_numeric($val) {

        if(is_numeric($val))
            return true;

    }

}

Would mean having to instantiate an instance of the class to use the functions - a pointless use of system memory, I'd have thought? :

$validator = new Validator();
if(!$validator->is_numeric($_POST['age'])) $error['age'] = "Age must be a number";

My example validation method is a poor example since it doesn't do anything than use the standard PHP is_numeric function, but this is just for the sake of illustrating my point.

Is the static method class the better option? If not, why?

Answer 1

I would suggest not only making your validation methods static, but also allowing instantiation of the class.

Lets pretend we call our class 'Field'. It would then be nice to have a constructor with the arguments: field_name, widget_type, validator_type and whatever else you want. then you can just make Field objects and call 'validate()' or some other similarly named function.

eg:

$email_field = new Field('Email','entry','email_validator');
$email_field.validate();

The constructor can then fetch it's value from the request variable, and the validate function will look for a static validator called 'email_validator'. even better would be to put the validator in the constructor...

Answer 2

I think, if you use more than one function calls on a specific instance of your validator class. It's best to use a singleton method or just create one instance (ie $validator = new Validator; );

Memory wise this would be the best choice, I'd say, if you have (let's say) 100 separate static calls to the class instead of 1 instance with 100 calls on that, you'd be better of creating a new instance.

Answer 3

Using a validator class seems to be the better choice for me. You can use it without instantiation, if there are no class variables needed. And if you need no longtime instance of that class, it won't need any space in the RAM.

Answer 4

Think about the maintainability and readability of your code. It's always tempting to build frameworks and classes and so on but embedding the same features in 100 LOC instead of 40 isn't always the good choice. The decision should depend on what your validator will do.

If it has no internal state, and no complex parameters, don't make classes.

A simple function would not only be simpler to analyze, it would let the user know that there is no side effect, that he doesn't have to read more documentation than the one of the function he intends to use.

Keep it simple.