Merge pull request #2 from sensorario/decorator

add new decorator pattern

Author: sensorario

structural/decorator/README.md

@@ -1,26 +1,28 @@
 # Decorator
 
-The decorator pattern provide a lot of benefits when working with legacy code. In this example I have a legacy code. For example a legacy recipe. A decorator add functionality. The functionality in this example is the method Decorate. In the real world Decorate() is represented by a method that must be decorate.
+The decorator pattern provide a lot of benefits when working with legacy code. In this example legacy code is represented by a legacy recipe. A decorator add functionality and in this example decorators are new ingredients.
 
 ```go
 type LegacyRecipe struct {
-	Decorate() (string, error)
 }
+```
+Starting from legacy code, we must have a default behavior. For example LegacyRecipe could have a method called `Decorate` that provide the recipe.
 
+```go
 func (lr *LegacyRecipe) Decorate() (string, error) {
-	return "Legacy recipe with the following ingredients:", nil
+	return "Original behavior: ", nil
 }
 ```
 
-All object needed to implement the decorator pattern should implement same interface.
+All object needed to implement the decorator pattern should implement same interface. Because of we must improve the functionality of `Decorate` method we'll create an interface like this.
 
 ```go
 type Decorable interface {
 	Decorate() (string, error)
 }
 ```
 
-Because of we are treating with a legacy recipe. All new ingredient must contains a `Decorable` recipe.
+And because of we are treating with a legacy recipe, all new ingredient must implement a `Decorable` interface.
 
 ```go
 type NewIngredient struct {
@@ -35,6 +37,12 @@ func (ni *NewIngredient) Decorate() (string, error) {
 	if err != nil {
 		return "", err
 	}
-	return fmt.Sprintf("%s %s,", s, "new ingredient"), nil
+	return fmt.Sprintf("%s %s,", s, "with decoration"), nil
 }
 ```
+As you can see we can use this decorator with:
+
+```go
+dec := &NewIngredient{&LegacyRecipe{}}
+dev.Decorate() // Original behavior: with decoration
+```