implemented bridge pattern

README.md

@@ -16,6 +16,7 @@
 - [Structural patterns](#structural-patterns)
     - [Composition](#composition)
     - [Adapter](#adapter)
+    - [Bridge](#bridge)
 - [Behavioral patterns](#behavioral-patterns)
     - [Chain of responsibility](#chain-of-responsibility)
     - [Strategy](#strategy)
@@ -58,6 +59,9 @@ lets clients treat individual objects and compositions of objects uniformly.
 Convert the interfac e of a class into another interface clients expect. Adapter lets
 classes work together that couldn' t otherwise because of incompatible interfaces.
 
+### Bridge
+Decouple an abstraction from its implementation so that the two can vary independently.
+
 ## Behavioral patterns
 Behavioral patterns are concerned with algorithms and the assignment of responsibilities
 between objects. Behavio ral patterns describe not just patterns of objects or classes

structural/bridge/bridge.go

@@ -0,0 +1,37 @@
+package bridge
+
+import "fmt"
+import "errors"
+
+// Bridge interface
+type Drawer interface {
+	DrawRectangle(w, h int) 
+}
+
+type GreenRectangleDrawer struct {}
+func (d GreenRectangleDrawer) DrawRectangle(w, h int) {
+	fmt.Printf("Green rectangle W: %d, H: %d", w, h)
+}
+
+type RedRectangleDrawer struct {}
+func (d RedRectangleDrawer) DrawRectangle(w, h int) {
+	fmt.Printf("Red rectangle W: %d, H: %d", w, h)
+}
+
+type Shape interface {
+	Draw() error
+}
+
+type Rectangle struct {
+	Width, Height int
+	drawer Drawer
+}
+
+func (d Rectangle) Draw () error {
+	if d.drawer == nil {
+		return errors.New("Drawer not initialized.")
+	}
+
+	d.drawer.DrawRectangle(d.Width, d.Height)
+	return nil
+}