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at-m42:lecture7 [2009/04/13 15:49] – eechrisat-m42:lecture7 [2009/04/13 16:01] – eechris
Line 645: Line 645:
   Game: Lord of the Rings   Game: Lord of the Rings
   ===========================   ===========================
-  MagicItem: Item: The One Ring has value 1000; potency: 500.+  MagicalItem: Item: The One Ring has value 1000; potency: 500.
   WeightyItem: Item: Rations has value 10; weight: 20.   WeightyItem: Item: Rations has value 10; weight: 20.
   Item: clay pipe has value 0   Item: clay pipe has value 0
Line 684: Line 684:
 class WeightyItem extends Item { ... } class WeightyItem extends Item { ... }
  
-class MagicItem extends Item { ... }+class MagicalItem extends Item { ... }
 </code> </code>
  
Line 719: Line 719:
   Game: Lord of the Rings   Game: Lord of the Rings
   ===========================   ===========================
-  MagicItem: Item: The One Ring has value 1000; potency: 500.+  MagicalItem: Item: The One Ring has value 1000; potency: 500.
   WeightyItem: Item: Rations has value 10; weight: 20.   WeightyItem: Item: Rations has value 10; weight: 20.
   WeightyItem: Item: Elvish Dagger has value 50; weight: 2.   WeightyItem: Item: Elvish Dagger has value 50; weight: 2.
Line 745: Line 745:
  
 <code groovy> <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)> <code groovy 1 | Example 15: The interface calls (at-m42/Examples/lecture07/example15.groovy)>
at-m42/lecture7.txt · Last modified: 2011/01/14 12:45 by 127.0.0.1