Merge pull request #27 from ismasan/import_mapper

HashMapper.import_mapper

README.md

@@ -306,6 +306,24 @@ EggMapper.normalize({}, options: { no_default: true })
 EggMapper.denormalize({fried: 4})
 ```
 
+#### Importing mappings from another mapper
+
+Use `.import_mapper(another_mapper)` to import mappings from another mapper. This is useful when you want to reuse mappings from another mapper.
+
+```ruby
+class Mapper1
+  extend HashMapper
+  map from('/name'), to('/name')
+end
+
+class Mapper2
+  extend HashMapper
+  import_mapper Mapper1
+  map from('/age'), to('/age')
+end
+
+# Mapper2 will have mappings from Mapper1 ('/name' => '/name') and its own mappings ('/age' => '/age')
+```
 
 ## REQUIREMENTS:
 

lib/hash_mapper.rb

@@ -71,6 +71,10 @@ def from(path, &filter)
     path_map
   end
 
+  def import_mapper(mapper)
+    self.maps = self.maps + mapper.maps.dup
+  end
+
   alias :to :from
 
   def using(mapper_class)

spec/hash_mapper_spec.rb

@@ -446,6 +446,25 @@ class DefaultValues
   end
 end
 
+describe '.import_mapper(another_mapper)' do
+  let(:mapper) do
+    Class.new do
+      extend HashMapper
+
+      import_mapper DefaultValues
+      map from('/name'), to('/nombre')
+    end
+  end
+
+  it 'imports the mappings from another mapper' do
+    expect(mapper.maps.size).to eq(3)
+    expect(mapper.normalize({
+      'without_default' => 'some_value',
+      'name' => 'ismael'
+    })).to eq({ not_defaulted: 'some_value', defaulted: 'the_default_value', nombre: 'ismael' })
+  end
+end
+
 class MultiBeforeFilter
   extend HashMapper