Hash extension with key and value mapper methods.

hash.rb

class Hash
 
  def map_keys
    Hash[self.map { |key, value| [yield(key), value] }]
  end
 
 
 
  def map_keys!
    keys.each { |key| self[yield(key)] = delete key }
    self
  end
 
 
 
  def map_values
    Hash[self.map { |key, value| [key, yield(value)] }]
  end
 
 
 
  def map_values!
    each { |key, value| self[key] = yield(value) }
    self
  end
 
end

hash_spec.rb

describe Hash do
 
  describe "#map_keys" do
 
    it "should return with a new Hash whose keys are mapped with the given block" do
      result = { key1: "value1" }.map_keys { |key| "#{key}_mapped".to_sym }
      result.should == { key1_mapped: "value1" }
    end
 
 
 
    it "should not change the original hash" do
      hash = { key1: "value1" }
      hash.map_keys { |key| "#{key}_mapped".to_sym }
      hash.should == { key1: "value1" }
    end
 
  end
 
 
 
  describe "#map_keys!" do
 
    it "should return with a Hash whose keys are mapped with the given block" do
      result = { key1: "value1" }.map_keys! { |key| "#{key}_mapped".to_sym }
      result.should == { key1_mapped: "value1" }
    end
 
 
 
    it "should change the Hash's keys with the given block" do
      hash = { key1: "value1" }
      hash.map_keys! { |key| "#{key}_mapped".to_sym }
      hash.should == { key1_mapped: "value1" }
    end
 
 
 
    describe "#map_values" do
 
      it "should return with a new Hash whose values are mapped with the given block" do
        result = { key1: "value1" }.map_values { |value| "#{value}_mapped" }
        result.should == { key1: "value1_mapped" }
      end
 
 
 
      it "should not change the original hash" do
        hash = { key1: "value1" }
        hash.map_values { |value| "#{value}_mapped" }
        hash.should == { key1: "value1" }
      end
 
    end
 
 
 
    describe "#map_values!" do
 
      it "should return with a Hash whose values are mapped with the given block" do
        result = { key1: "value1" }.map_values! { |value| "#{value}_mapped" }
        result.should == { key1: "value1_mapped" }
      end
 
 
 
      it "should change the Hash's values with the given block" do
        hash = { key1: "value1" }
        hash.map_values! { |value| "#{value}_mapped" }
        hash.should == { key1: "value1_mapped" }
      end
 
    end
 
  end
 
end