Question

I have table called posts in my DB. Each post has field called social_network

When I get all posts into array in my code I need to create instances for each one based on it’s social_network field.

Right now I use switch statement for this but I don’t like it as it is not flexible.

$posts = DataBase::getPosts(); // pseudocode
foreach($posts as $post) {
  switch($post->getSocialNetwork()){
    case 'Facebook':
      $social = new FacebookPost($post->getId());
      break;
    case 'Twitter':
      $social = new TwitterPost($post->getId());
      break;        
    // .... other social networks
  }
}

Answer 1

Add an interface to the classes FacebookPost and TwitterPost (eg SocialPostInterface) that has defined same basic necessary methods like getId(), postToNetwork() Then you can add as many new social networks as you want, without having to change this piece of code. They just have to implement the interface

Then experience the power of polymorhpism:

foreach ($posts as $post) {
    $className = $post->getSocialNetwork() . 'Post';
    // lets check if such class exists
    if (!class_exists($className, false /* do not attempt autoload */)) {
        throw new Exception("Unknown social network post class $className");
    }
    $social = new $className($post->getId());
    $social->doSomeStuffThatTheInterfaceHasDeclared();
}