Add explicit and default values for keys.

lib/between/key.rb

@@ -9,20 +9,25 @@ def initialize name, context, data, options = nil
 
       @context = context
       @data    = data
+      @default = options && options[:default]
       @source  = (options && options[:from]) || name
       @target  = name.intern
-    end
-
-    def get
-      @data[@source] || @data[@source.to_s]
+      @value   = options && options[:value]
     end
 
     def exists?
-      @data.include?(@source) || @data.include?(@source.to_s)
+      !!(@value || @data.include?(@source) ||
+         @data.include?(@source.to_s) || @default)
     end
 
     def set
-      @context.set @target, get
+      @context.set @target, value
+
+      value
+    end
+
+    def value
+      @value ||= @data[@source] || @data[@source.to_s] || @default
     end
   end
 end

test/between_parser_test.rb

@@ -40,5 +40,26 @@
 
       p.key :foo, :from => :baz
     end
+
+    it "can specify an explicit override value" do
+      ctx = mock { expects(:set).with :foo, "bar" }
+      p   = Between::Parser.new ctx, "foo" => "baz"
+
+      p.key :foo, :value => "bar"
+    end
+
+    it "can specify a default value" do
+      ctx = mock { expects(:set).with :foo, "bar" }
+      p   = Between::Parser.new ctx
+
+      p.key :foo, :default => "bar"
+    end
+
+    it "returns the value set on the context" do
+      ctx = stub :set
+      p   = Between::Parser.new ctx, "foo" => "bar"
+
+      assert_equal "bar", p.key(:foo)
+    end
   end
 end