Add #replace to Hashie::Dash to achieve Hash-like behavior

2 files changed, 20 insertions, 0 deletions

diff --git a/lib/hashie/dash.rb b/lib/hashie/dash.rb
index 8a1f6f7..ccee9aa 100644
--- a/lib/hashie/dash.rb
+++ b/lib/hashie/dash.rb
@@ -127,6 +127,12 @@ module Hashie
       super(property.to_s, value)
     end
 
+    def replace(other_hash)
+      other_hash = other_hash.merge(self.class.defaults)
+      (keys - other_hash.keys).each { |key| delete(key) }
+      other_hash.each { |key, value| self[key] = value }
+    end
+
     private
 
       def initialize_attributes(attributes)
diff --git a/spec/hashie/dash_spec.rb b/spec/hashie/dash_spec.rb
index 1e1edc9..008f608 100644
--- a/spec/hashie/dash_spec.rb
+++ b/spec/hashie/dash_spec.rb
@@ -170,6 +170,20 @@ describe DashTest do
       described_class.defaults.should == { :count => 0 }
     end
   end
+
+  describe '#replace' do
+    before { subject.replace(:first_name => "Cain") }
+
+    it 'sets all specified keys to their corresponding values' do
+      subject.first_name.should == "Cain"
+    end
+
+    it 'leaves only specified keys and keys with default values' do
+      subject.keys.should == ['first_name', 'count']
+      subject.email.should be_nil
+      subject.count.should == 0
+    end
+  end
 end
 
 describe Hashie::Dash, 'inheritance' do