strategy.md

Strategy design pattern

Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from the clients that use it. Capture the abstraction in an interface, bury implementation details in derived classes.

A Strategy defines a set of algorithms that can be used interchangeably. Modes of transportation to an airport is an example of a Strategy. Several options exist such as driving one's own car, taking a taxi, an airport shuttle, a city bus, or a limousine service. Any of these modes of transportation will get a traveler to the airport, and they can be used interchangeably. The traveler must chose the Strategy based on trade-offs between cost, convenience, and time.

<?php

class StrategyContext {
    private $strategy = NULL; 
    //bookList is not instantiated at construct time
    public function __construct($strategy_ind_id) {
        switch ($strategy_ind_id) {
            case "C": 
                $this->strategy = new StrategyCaps();
            break;
            case "E": 
                $this->strategy = new StrategyExclaim();
            break;
            case "S": 
                $this->strategy = new StrategyStars();
            break;
        }
    }
    public function showBookTitle($book) {
      return $this->strategy->showTitle($book);
    }
}

interface StrategyInterface {
    public function showTitle($book_in);
}
 
class StrategyCaps implements StrategyInterface {
    public function showTitle($book_in) {
        $title = $book_in->getTitle();
        $this->titleCount++;
        return strtoupper ($title);
    }
}

class StrategyExclaim implements StrategyInterface {
    public function showTitle($book_in) {
        $title = $book_in->getTitle();
        $this->titleCount++;
        return Str_replace(' ','!',$title);
    }
}

class StrategyStars implements StrategyInterface {
    public function showTitle($book_in) {
        $title = $book_in->getTitle();
        $this->titleCount++;
        return Str_replace(' ','*',$title);
    }
}

class Book {
    private $author;
    private $title;
    function __construct($title_in, $author_in) {
        $this->author = $author_in;
        $this->title  = $title_in;
    }
    function getAuthor() {
        return $this->author;
    }
    function getTitle() {
        return $this->title;
    }
    function getAuthorAndTitle() {
        return $this->getTitle() . ' by ' . $this->getAuthor();
    }
}

  writeln('BEGIN TESTING STRATEGY PATTERN');
  writeln('');

  $book = new Book('PHP for Cats','Larry Truett');
 
  $strategyContextC = new StrategyContext('C');
  $strategyContextE = new StrategyContext('E');
  $strategyContextS = new StrategyContext('S');
 
  writeln('test 1 - show name context C');
  writeln($strategyContextC->showBookTitle($book));
  writeln('');

  writeln('test 2 - show name context E');
  writeln($strategyContextE->showBookTitle($book));
  writeln('');
 
  writeln('test 3 - show name context S');
  writeln($strategyContextS->showBookTitle($book));
  writeln('');

  writeln('END TESTING STRATEGY PATTERN');

  function writeln($line_in) {
    echo $line_in."<br/>";
  }

?>

Outputs:

BEGIN TESTING STRATEGY PATTERN

test 1 - show name context C
PHP FOR CATS

test 2 - show name context E
PHP!for!Cats

test 3 - show name context S
PHP*for*Cats

END TESTING STRATEGY PATTERN