/interpreter/tags/at2dist090708/src/edu/vub/at/exceptions/XSelectorNotFound.java

  1/**
  2 * AmbientTalk/2 Project
  3 * XSelectorNotFound.java created on Jul 23, 2006 at 3:20:22 PM
  4 * (c) Programming Technology Lab, 2006 - 2007
  5 * Authors: Tom Van Cutsem & Stijn Mostinckx
  6 * 
  7 * Permission is hereby granted, free of charge, to any person
  8 * obtaining a copy of this software and associated documentation
  9 * files (the "Software"), to deal in the Software without
 10 * restriction, including without limitation the rights to use,
 11 * copy, modify, merge, publish, distribute, sublicense, and/or
 12 * sell copies of the Software, and to permit persons to whom the
 13 * Software is furnished to do so, subject to the following
 14 * conditions:
 15 *
 16 * The above copyright notice and this permission notice shall be
 17 * included in all copies or substantial portions of the Software.
 18 *
 19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 21 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 23 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 24 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 25 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 26 * OTHER DEALINGS IN THE SOFTWARE.
 27 */
 28package edu.vub.at.exceptions;
 29
 30import edu.vub.at.objects.ATObject;
 31import edu.vub.at.objects.ATTypeTag;
 32import edu.vub.at.objects.coercion.NativeTypeTags;
 33import edu.vub.at.objects.grammar.ATSymbol;
 34
 35/**
 36 * XSelectorNotFound is thrown during lookup when a particular slot cannot be found. It is 
 37 * equipped with a dedicated constructor to allow diagnosing the underlying problem.
 38 * 
 39 * @author smostinc
 40 */
 41public class XSelectorNotFound extends InterpreterException {
 42
 43	private static final long serialVersionUID = -9186247764999498158L;
 44	
 45	private final ATSymbol selector_;
 46	private final ATObject inObject_;
 47	
 48	/**
 49	 * Constructor reporting that a particular slot could not be found.
 50	 * @param selector the name of the slot being sought for.
 51	 * @param inObject the object from which the slot was being selected.
 52	 */
 53	public XSelectorNotFound(ATSymbol selector, ATObject inObject) {
 54		selector_ = selector;
 55		inObject_ = inObject;
 56	}
 57	
 58	public String getMessage() {
 59		String obj;
 60		try {
 61			obj = inObject_.meta_print().javaValue;
 62		} catch(InterpreterException e) {
 63			obj = "<unprintable object: "+e.getMessage()+">";
 64		}
 65		return "Lookup failure : selector " + selector_ + " could not be found in "+ obj;
 66	}
 67	
 68	public ATTypeTag getType() {
 69		return NativeTypeTags._SELECTORNOTFOUND_;
 70	}
 71	
 72	/**
 73	 * Rethrows the exception unless the missing selector equals the one given in this method. Rationale:
 74	 * Several meta_* methods actually catch this exception to recover from a failed lookup by continuing
 75	 * the search in an other object (e.g. parent objects, native objects, ...). When the lookup would
 76	 * succeed and an XSelectorNotFound exception is raised because of another failed lookup, this alternate
 77	 * behaviour should not be tried. Hence, when catching an XSelectorNotFound with the intention of redirecting
 78	 * lookup, the exception handler should invoke this method to ensure that he is dealing with the right exception.
 79	 */
 80	public void catchOnlyIfSelectorEquals(ATSymbol sym) throws InterpreterException {
 81		if (!selector_.equals(sym)) {
 82			throw this;
 83		}
 84	}
 85
 86	/**
 87	 * @return the selector that could not be located.
 88	 */
 89	public ATSymbol getSelector() {
 90		return selector_;
 91	}
 92
 93	/**
 94	 * @return the object in which the selector could not be located.
 95	 */
 96	public ATObject getInObject() {
 97		return inObject_;
 98	}
 99	
100}