Extension methods implementation revamped

at 2010-08-18 in RFCs, 5.8-SERIES by friebe (0 comments)

Just shortly after announcing the removal of the original extension methods implementation we have now come up with a faster, less-clumsy and well-behaving extension method implementation - and have reactivated the corresponding RFC, scheduled for implementation in SVN next week.

Declaration of an extension class is done as follows:

  class ArrayListExtensions extends Object {
    
    static function __import($scope) {
      xp::extensions(__CLASS__, $scope);
    }
    
    /**
     * ArrayList::map() extension
     *
     * @param   lang.types.ArrayList self
     * @return  lang.types.ArrayList mapped
     */
    public static function map(ArrayList $self, $block) {
      $mapped= ArrayList::newInstance($self->length);
      foreach ($self->values as $i => $value) {
        $mapped[$i]= $block($value);
      }
      return $mapped;
    }

So the only thing necessary is registering extension methods from this class inside the __import() handler which is called on scope-import (via uses()). Note that only static methods whose first parameter is named self are valid extension methods. Of course the class may have any other number of non-extension methods.

To use extension methods simply add the extension class to the uses() statement of the scope you want to use them in:

  uses('com.example.extensions.ArrayListExtensions');
  
  class ArrayListDemo extends Object {
    
    /**
     * Main method
     *
     * @param   string[] args
     */
    public static function main($args) {
      $sorted= ArrayList::newInstance($args)->sorted();
      Console::writeLine('sorted()= ', $sorted);
    }
  }

This will be the output:

  $ xp com.example.ArrayListDemo World Hello
sorted()= lang.types.ArrayList[2]@{"Hello", "World"}

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