Add transfer() utility function.

2 files changed, 25 insertions, 3 deletions

diff --git a/weatbag/tiles/e1.py b/weatbag/tiles/e1.py
index 909f1b3..486a98f 100644
--- a/weatbag/tiles/e1.py
+++ b/weatbag/tiles/e1.py
@@ -1,4 +1,5 @@
 from weatbag import words
+from weatbag.utils import transfer
 
 class Tile:
     def __init__(self):
@@ -17,9 +18,7 @@ class Tile:
             print("Sorry, I don't understand.")
     
     def take_berries(self, player):
-        if self.contents['berries'] > 0:
-            self.contents['berries'] -= 1
-            player.give('berries')
+        if transfer('berries', self.contents, player.inventory):
             print("Reaching up, you pick the berries.")
         else:
             print("There are no berries here.")
diff --git a/weatbag/utils.py b/weatbag/utils.py
new file mode 100644
index 0000000..0f73294
--- /dev/null
+++ b/weatbag/utils.py
@@ -0,0 +1,23 @@
+"""Utility functions for the game."""
+
+def transfer(item, from_collection, to_collection, n=1):
+    """Move an item from one dictionary of objects to another.
+    
+    Returns True if the item was successfully transferred, False if it's not in
+    from_collection.
+    
+    For example, to have the player pick up a pointy stick::
+    
+        if transfer('pointy stick', tile.contents, player.inventory):
+            print("You take the stick.")
+        else:
+            print("There's no stick here.")
+    """
+    if from_collection.get(item, 0) < n:
+        return False
+    from_collection[item] -= n
+    if item in to_collection:
+        to_collection[item] += n
+    else:
+        to_collection[item] = n
+    return True