Mapping numeric score to feedback message in PHP

Created:06 Sep 2017 23:04:22 , in  Web development

The other day I coded a sort of game in PHP programming language. One of it's features is a final score pop-up message, which consists of three parts. They are a number, a percent and a few words of a humoristic player performance feeback. The feedback is based upon the number or the percent the player scores.

When I first looked at how to design that sort of functionality, I thought, a simple mapping from a number to a string would suffice.

You provide some feedback in the form of a string for lets say score of 20%. When the score is 20%, a player is shown the message. There is a small trouble with this solution, though. In all but the simplest cases, the score can be anything between 0% and 100% inclusive, perhaps 19.53% or 20.0091% instead of 20%, you have prepared a feedback for. It looks like the basic idea misfires for all but few cases here.

A better, functional design is not far away, though. It is based on the idea of mapping intervals rather than numbers to strings. In short, SWWWScoreFeedback, a tiny PHP programming language class, does exactly this sort of thing.

Here is the code:

/*
  Class: SWWWScoreFeedback 
  Description: Get feedback based on score
  Author: Sylwester Wojnowski
  WWW: wojnowski.net.pl

  Methods:
    instnce($conf) - public static - get instance of SWWWScoreFeedback
      parameters:
        $conf - array - associative array of scores/messages
        return - object - instance of SWWWScoreFeedback
        
    get($score) - public - get feedback message
      parameters: 
        $score - number|string - number or percent in range 0 - 100 inclusive
        [$func] - function - callback function
      return - string - feedback for the score
*/
class SWWWScoreFeedback{

  const NO_FEEDBACK = 'No feedbacks added.';
  const NO_LOWEST_BOUND_FEEDBACK = 'Lowest score bound feedback not specified.';
  const SCORE_OUT_OF_RANGE = 'Score should be in range 0 through 100.';

  private $feedback = array();
  
  public static function instance($conf){
    return new SWWWScoreFeedback($conf);
  }
  
  public function __construct($conf){
    if(!$this -> insert($conf)){
      throw new Exception(self::NO_FEEDBACK);
    }
    if( ! array_key_exists(0,$this -> feedback) ){
      throw new Exception(self::NO_LOWEST_BOUND_FEEDBACK);
    }
  }
  
  // add scores and feedbacks for them
  private function insert($feedback){
    foreach($feedback as $k => $v){
      $ck = (int)str_replace('%','',$k);
      if($ck >= 0 or $ck <= 100){
        $this -> feedback[$ck] = $v;  
      }
    }
    return empty($this -> feedback) ? false : true;
  }
  
  // get feedback based on score provided
  public function get($score){
    $cscore = (int)str_replace('%','',$score);
    $ck = null;
    if($cscore >= 0 and $cscore <= 100){
      if(array_key_exists($cscore,$this -> feedback)){
        $ck = $cscore;  
      }else{
        foreach($this -> feedback as $k => $f){
          if($cscore > $k){
            $ck = $k;
          }else{
            break; 
          }
        }
      }     
    }else{
      throw new OutOfRangeException(self::SCORE_OUT_OF_RANGE);
    }   
    return $this -> feedback[$ck];
  }
}

SWWWScoreFeedback configuration

SWWWScoreFeedback should be configured by passing an associative array before it can be used. Keys of such an array are either numbers or percents (given as strings) in range from 0 to 100, with 0 the only key required. These keys are used to build intervals then. Values are strings representing feedback. There is no restriction on number of key / value pairs in the configuration array. Also, real numbers are as good as intergers for case.

 
$conf = array(
  0 => 'Terrible!',
  25 => 'You do not want to remember this!',
  51 => 'You have passed, but only just.',
  75 => 'Decent score!',
  100 => 'Congratulations, this is a perfect score!' 
);

In the above example, the intervals would be [0,25),[25,51),[51,75),[75,100),[100,100].

Once the configuration array is ready, you pass it to instance method of SWWWScoreFeedback and obtain an object.

$instance = SWWWScoreFeedback::instance($conf);      

Getting feedback based on score

The object has just one public method called get. Get, when passed a number in range from 0 to 100 (or a percent) returns a string.

Here are some examples:

$instance -> get(0);
=> 'Terrible!'

$instance -> get('90.23%');
=> 'Decent score!'

$instance -> get(100);
=> 'Congratulations, this is a perfect score!'

Final thoughts

Regardless of programming language, mapping numbers to numbers, strings, functions or objects is a frequent task in computer programming. The need of mapping intervals crops up less frequently, still the technique is extremely useful for solving coding tasks like the one described in this text and many other, hence worth of spending some time on.

I hope the article was enjoyable and code in it simple enough to follow.

This post was updated on 09 Sep 2017 21:12:07

Tags:  php