ERXComparatorSelector.java

package er.extensions.foundation;

import java.lang.reflect.InvocationTargetException;
import java.util.Comparator;

import com.webobjects.foundation.NSSelector;

/**
 * <p>
 * ERXComparatorSelector allows you to pass an arbitrary Comparator instance as an NSSelector into EOSortOrdering for use
 * with an in-memory sort. Note that this WILL NOT work for sorting directly in the database. This exploits the fact 
 * that EOSortOrdering calls selector.invoke(left, right) when you pass it an arbitrary selector to use.
 * </p>
 * 
 * <pre>
 * Example: ERXArrayUtilities.sortedArraySortedWithKey(array, "someKey", new ERXComparatorSelector(Collator.getInstance()))
 * </pre>
 * 
 * @author mschrag
 */
public class ERXComparatorSelector extends NSSelector {
	/**
	 * Do I need to update serialVersionUID?
	 * See section 5.6 <cite>Type Changes Affecting Serialization</cite> on page 51 of the 
	 * <a href="http://java.sun.com/j2se/1.4/pdf/serial-spec.pdf">Java Object Serialization Spec</a>
	 */
	private static final long serialVersionUID = 1L;

	private Comparator _comparator;
	
	/**
	 * Constructs a new ERXComparatorSelector.
	 * 
	 * @param comparator the backing comparator to sort with 
	 */
	public ERXComparatorSelector(Comparator comparator) {
		super("ERXComparatorSelector:" + comparator.getClass().getSimpleName(), null);
		_comparator = comparator;
	}
	
	@Override
	public Object invoke(Object target, Object argument) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchMethodException {
		return Integer.valueOf(_comparator.compare(target, argument));
	}
}