/interpreter/tags/at2dist130208/src/edu/vub/at/objects/natives/NATField.java

  1/**
  2 * AmbientTalk/2 Project
  3 * NATField.java created on Jul 27, 2006 at 2:27:53 AM
  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.objects.natives;
 29
 30import edu.vub.at.exceptions.InterpreterException;
 31import edu.vub.at.exceptions.XIllegalOperation;
 32import edu.vub.at.exceptions.XSelectorNotFound;
 33import edu.vub.at.exceptions.XTypeMismatch;
 34import edu.vub.at.objects.ATField;
 35import edu.vub.at.objects.ATObject;
 36import edu.vub.at.objects.ATTable;
 37import edu.vub.at.objects.coercion.NativeTypeTags;
 38import edu.vub.at.objects.grammar.ATSymbol;
 39
 40/**
 41 * NATField implements a causally connected field of an object. Rather than storing
 42 * these fields directly in every object, we choose to only make people pay when they
 43 * choose to reify them. 
 44 * 
 45 * @author smostinc, tvcutsem
 46 */
 47public class NATField extends NATByRef implements ATField {
 48
 49	private final ATSymbol name_;
 50	private final ATObject host_;
 51	
 52	/**
 53	 * Constructs a new native field object linked to the field of a base-level
 54	 * AmbientTalk object
 55	 */
 56	public NATField(ATSymbol name, ATObject host) {
 57		name_ = name;
 58		host_ = host;
 59	}
 60
 61	public ATSymbol base_name() {
 62		return name_;
 63	}
 64
 65	public ATObject base_readField() throws InterpreterException {
 66		try {
 67			return host_.meta_invokeField(host_, name_);
 68		} catch (XSelectorNotFound e) {
 69			e.catchOnlyIfSelectorEquals(name_);
 70			// Since the field was selected from the receiver, it should always be found
 71			throw new XIllegalOperation("Incorrectly initialised field accessed", e);
 72		}
 73	}
 74
 75	public ATObject base_writeField(ATObject newValue) throws InterpreterException {
 76		return host_.meta_invoke(host_, name_.asAssignmentSymbol(), NATTable.of(newValue));
 77	}
 78	
 79	public NATText meta_print() throws InterpreterException {
 80		return NATText.atValue("<field:"+name_.meta_print().javaValue+">");
 81	}
 82	
 83    public boolean isNativeField() {
 84        return true;
 85    }
 86
 87	public ATField asField() throws XTypeMismatch {
 88		return this;
 89	}
 90	
 91	/**
 92	 * Fields can be re-initialized when installed in an object that is being cloned.
 93	 * They expect the new owner of the field as the sole instance to their 'new' method
 94	 */
 95	public ATObject meta_newInstance(ATTable initargs) throws InterpreterException {
 96		if (initargs.base_length() != NATNumber.ONE) {
 97			return super.meta_newInstance(initargs);
 98		} else {
 99			ATObject newhost = initargs.base_at(NATNumber.ONE);
100			return new NATField(name_, (NATCallframe) newhost);
101		}
102	}
103	
104    public ATTable meta_typeTags() throws InterpreterException {
105    	return NATTable.of(NativeTypeTags._FIELD_);
106    }
107
108}