Undefined variable error in ExpressionEngine plugin - expressionengine

Question

I'm working on a plugin that does device detection based on an external library.
This is what I have so far:
class Deetector {
// public $return_data;
/**
* Constructor
*/
public function __construct()
{
$this->EE =& get_instance();
$this->EE->load->add_package_path(PATH_THIRD.'/deetector');
$this->EE->load->library('detector');
$this->return_data = "";
}
public function deetector()
{
return $ua->ua;
}
public function user_agent()
{
return $ua->ua;
}
// ----------------------------------------------------------------
/**
* Plugin Usage
*/
public static function usage()
{
ob_start();
$buffer = ob_get_contents();
ob_end_clean();
return $buffer;
}
}
If I call {exp:deetector} I get no output in the template. If I call {exp:deetector:user_agent} I get Undefined variable: ua.
Ultimately I don't plan on setting up different functions for each of the variables that the Detector library returns but am just trying to get it to output something at the moment.
I had originally started doing this as an extension which added the Detector library's variables to the global variables array and that was working fine; it's only since trying to do it as a plugin that I've run into problems.

Answer 1

You haven't set $this->ua to anything. I assume it's a variable of the detector library you loaded, so you probably want to do something like this:
class Deetector {
public function __construct()
{
$this->EE =& get_instance();
// remove this line, it's probably not doing anything
// $this->EE->load->add_package_path(PATH_THIRD.'/deetector');
$this->EE->load->library('detector');
// note you use $this->return_data instead of "return blah" in the constructor
$this->return_data = $this->EE->detector->ua;
}
// remove this, you can't have both __construct() and deetector(), they mean the same thing
// public function deetector()
// {
// return $ua->ua;
// }
public function user_agent()
{
return $this->EE->detector->ua;
}
}
UPDATE:
I took a look at the Detector docs, and it doesn't follow normal library conventions (it defines the $ua variable when you include the file). For that reason you should ignore the standard EE load functions, and include the file directly:
class Deetector {
public function __construct()
{
$this->EE =& get_instance();
// manually include the detector library
include(PATH_THIRD.'/deetector/libraries/detector.php');
// save the local $ua variable so we can use it in other functions further down
$this->ua = $ua;
// output the user agent in our template
$this->return_data = $this->ua->ua;
}
}