lib/hashery/static_hash.rb in hashery-1.4.0 vs lib/hashery/static_hash.rb in hashery-1.5.0

@@ -1,47 +1,94 @@
-require 'hashery/statichash'
+# = StaticHash
+#
+# A Hash object which raises an error if any
+# previously-defined key attempts to be set again.
+#
+# == Synopsis
+#
+#   foo = StaticHash.new
+#   foo['name'] = 'Tom'    #=> 'Tom'
+#   foo['age']  = 30       #=> 30
+#   foo['name'] = 'Bob'
+#
+# _produces_
+#
+#   ArgumentError: Duplicate key for StaticHash -- 'name'
+#
+# == Credit
+#
+# StaticHash has it's orgins in Gavin Kistner's WriteOnceHash
+# class found in his +basiclibrary.rb+ script.
+
+class StaticHash < Hash
+
+  # Set a value for a key. Raises an error if that key already
+  # exists with a different value.
+
+  def []=(key, value)
+    if key?(key) && self[key] != value
+      raise ArgumentError, "Duplicate key for StaticHash -- #{key.inspect}"
+    end
+    super(key, value)
+  end
+
+  #
+  def update(hash)
+    dups = (keys | hash.keys)
+    if dups.empty?
+      super(hash)
+    else
+      raise ArgumentError, "Duplicate key for StaticHash -- #{dups.inspect}"
+    end
+  end
+
+  #
+  alias_method :merge!, :update
+
+end
+