Question

If I have a class that will be instantiated that needs to reference data and/or functions that will be the same for each class. How should this be handled to follow proper programming practices

Example (in PHP):

class Column {
    $_type = null;
    $_validTypes = /* Large array of type choices */;

    public function __construct( $type ) {
        if( type_is_valid( $type ) ) {
             $_type = $type;
        }
    }

    public function type_is_valid( $type ) {
        return in_array( $type, $_validTypes );
    }
}

Then every time a Column is created, it will hold the $_validTypes variable. This variable only really needs to be defined once in memory where all Columns created could refer to a static function type_is_valid for a static class which would hold the $_validTypes variable, declared only once.

Is the idea of a static class, say ColumnHelper or ColumnHandler a good way to handle this? Or is there a way to hold static data and methods within this class? Or is this redefining of $_validTypes for each Column an okay way to do things?

Answer 1

One option would be create a new model for the column configuration e.g.

class ColumnConfig {
    private $validTypes;
    public isValid($type){
        return isset($this->validType($type))?true:false;
    }
}

then either add it once to API if you have one, or create one global instance e.g.

$cc = new ColumnConfig();
class Column {
    private $cc;
    function __construct($type){
        $this->cc = $this->api->getCC(); // if you have api
        global $cc; // assuming you have no api, an you create a global $cc instance once.
        $this->cc = $cc; // <-- this would pass only reference to $cc not a copy of $cc itself.

        if ($this->cc->isValid($type)){
          ....
        }
    }
}

Sounds like way to go.