Constructor Overloading
- by Mark Baker
Normally when I want to create a class constructor that accepts different types of parameters, I'll use a kludgy overloading principle of not defining any args in the constructor definition:
e.g. for an ECEF coordinate class constructor, I want it to accept either $x, $y and $z arguments, or to accept a single array argument containg x, y and z values, or to accept a single LatLong object I'd create a constructor looking something like:
function __construct()
{
// Identify if any arguments have been passed to the constructor
if (func_num_args() > 0) {
$args = func_get_args();
// Identify the overload constructor required, based on the datatype of the first argument
$argType = gettype($args[0]);
switch($argType) {
case 'array' :
// Array of Cartesian co-ordinate values
$overloadConstructor = 'setCoordinatesFromArray';
break;
case 'object' :
// A LatLong object that needs converting to Cartesian co-ordinate values
$overloadConstructor = 'setCoordinatesFromLatLong';
break;
default :
// Individual Cartesian co-ordinate values
$overloadConstructor = 'setCoordinatesFromXYZ';
break;
}
// Call the appropriate overload constructor
call_user_func_array(array($this,$overloadConstructor),$args);
}
} // function __construct()
I'm looking at an alternative: to provide a straight constructor with $x, $y and $z as defined arguments, and to provide static methods of createECEFfromArray() and createECEFfromLatLong() that handle all the necessary extraction of x, y and z; then create a new ECEF object using the standard constructor, and return that
Which option is cleaner from an OO purists perspective?
