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--- at-m42:lecture7 [2009/04/13 15:50] – eechris
+++ at-m42:lecture7 [2011/01/14 12:45] (current) – external edit 127.0.0.1
@@ Line 745: / Line 745: @@
 <code groovy>
-interface portable {
+interface Portable {
+    Boolean abstract canCarry(Player player)
-    Boolean abstract canCarry(Player player)  // deferred method
 }
-abstract class AbstractItem implements portable {
+abstract class AbstractItem implements Portable { ... }
-    String toString() { 							// redefinition
+class WeightyItem extends AbstractItem { ... }
-        return "Item: ${name} has value ${value}"
-    }
-    Boolean hasDescription() {
-        return ! (description == '')
-    }
-    Boolean canCarry(Player player)  	{				// redefinition
-    	return (player.funds >= value)
-    }
-// ----- properties ----------------------------------
+class MagicalItem extends AbstractItem { ... }
+</code>
-    def name  // name of the item
+Full listing for [[http://www.cpjobling.org.uk/~eechris/at-m42/Examples/lecture07/example15.groovy|Example 15]] is given in the notes.
-    def value // value of the item in game points
-    def description = '' // a description of the item
-}
+----
-class WeightyItem extends AbstractItem {
+The implementation for this is give in Example 15, where ''Portable'' is introduced as a an interface class. An interface declares, but does not define, one or more abstract methods. The abstract class ''AbstractItem'' conforms to the protocol since it //implements// the ''Portable// interface. Notice that ''AbstractItem'' offers a simple implementation for the ''canCarry'' method. We must explicitly redefine it in the ''WeightyItem'' and ''MigicalItem'' classes (note we use the superclass definitions in both!).
-    String toString() {
-        return 'WeightyItem: ' + super.toString() + "; weight: ${weight}."
-    }
-    Boolean canCarry(Player player) {
-    	return super.canCarry(player) && (weight < player.strength)
-    }
-// ---- properties -------------------------
-    def weight = 0
-}
-class MagicalItem extends AbstractItem {
-    String toString() {
-        return 'MagicalItem: ' + super.toString() + "; potency: ${potency}."
-    }
-    Boolean canCarry(Player player) {
-    	return super.canCarry(player) && (player.power >= (potency/5))
-    }
-</code>
 <code groovy 1 | Example 15: The interface calls (at-m42/Examples/lecture07/example15.groovy)>