Validation in a class inheritance hierachy

[lundberg]

Hello everyone,

If I've got a inheritance hierachy like "Field < StringField < EmailField" and I want to be able to have some validation logic in all of them with different generalization.

Field for example can check if a field is empty (required), StringField can check max/min length, etc. Now I want to be able to run $field->validate() and it will all be checked. Is it possible?

Thanks,

[Stormrider]

You could override the method in each of the inheriting classes to run the parent's validate method, and then add its own specific code.

class Field {
 public function validate () {
  //Generic field validation, store result in $blnValidated

  return $blnValidated;
 }//function
}//class

class StringField extends Field {
 public function validate () {
  //Validate string, store result in $blnValidated

  return ($blnValidated && parent::validate());
 }//function
}//class

class EmailField extends StringField {
 public function validate () {
  //Validate email, store result in $blnValidated

  return ($blnValidated && parent::validate());
 }//function
}//class

$field = new EmailField();
$blnValid = $field->validate(); 

Probably needs a bit of work though!

[AnthonySterling]

Check out this post here, it addresses exactly what you're after.

[lundberg]

Check out this post here, it addresses exactly what you're after.

I started out by using polymorphism solution where the base class constructor ran an init method but if I've got the inheritance hierarchy I wrote, if I create a EmailField the Field constructor will be run and it will call init which will call the init function in EmailField but not in the StringField.

The thing is that I want all the classes to add to an array in the base class called options. For example Field adds $this->options["required"] = true, StringField adds $this->options["max_length"] = some default value, etc. When a field is created you can send in an assoc array which changes the options. Then when I run validate it should all be validated.

Right now most of the code is in the base class and the sub-classes mostly add to the options array and create their validate class.

Hope I'm not making a mess of trying to describe what I want.

[Stormrider]

If you want to run the parent class's constructor, you have to explicitly call it with parent::__construct()

[lundberg]

Yeah, right now the StringField class looks like this:

class StringField extends Field
{
    public function __construct()
    {
        // Declare options and their default value
        $this->options["max_length"] = null;
        $this->options["min_length"] = null;

        // Call parent constructor
        if (is_array(@func_get_arg(0)))
            parent::__construct(@func_get_arg(0));
        else
            parent::__construct();
    }

    protected function validate()
    {
        // First let the parent class make more general validation
        if (!parent::validate())
            return false;

        // If the value is longer then the maximum length
        if (!is_null($this->options["max_length"]) && $this->value > $this->options["max_length"])
        {
            $this->validation_error = "##validationError.ExceededMaximumLength##";
        }

        // If the value is shorter then the minimum length
        if (!is_null($this->options["min_length"]) && $this->value < $this->options["min_length"])
        {
            $this->validation_error = "##validationError.DeceededMinimumLength##";
        }

        return empty($this->validation_error);
    }
} 

I don't like that I have to do the last part in the constructor and the first part in validate function. I want a nicer way of doing this Maybe I need to rethink the whole design.