add adapter pattern

Author: sensorario

README.md

@@ -13,3 +13,4 @@
 
  * [Composite](structural/composite) [:notebook:](http://en.wikipedia.org/wiki/Composite_pattern)
  * [Binary Tree compositions](structural/binary-tree-compositions) [:notebook:](https://en.wikipedia.org/wiki/Binary_tree)
+ * [Adapter](structural/adapter) [:notebook:](https://en.wikipedia.org/wiki/Adapter)

structural/adapter/adapter.go

@@ -0,0 +1,38 @@
+package main
+
+import "fmt"
+
+type LegacyPrinter interface {
+	Print(s string) string
+}
+
+type MyLegacyPrinter struct{}
+
+type ModernPrinter interface {
+	PrintStored() string
+}
+
+type PrinterAdapter struct {
+	OldPrinter LegacyPrinter
+	Msg        string
+}
+
+func (p *PrinterAdapter) PrintStored() (newMsg string) {
+	if p.OldPrinter != nil {
+		newMsg = fmt.Sprintf("Adapter: %s", p.Msg)
+		newMsg = p.OldPrinter.Print(newMsg)
+	} else {
+		newMsg = p.Msg
+	}
+	return
+}
+
+func (l *MyLegacyPrinter) Print(s string) (newMsg string) {
+	newMsg = fmt.Sprintf("Legacy Printer: %s\n", s)
+	println(newMsg)
+	return
+}
+
+func main() {
+	fmt.Println("vim-go")
+}

structural/adapter/adapter_test.go

@@ -0,0 +1,15 @@
+package main
+
+import "testing"
+
+func TestAdater(t *testing.T) {
+	msg := "Hello world!!!"
+	adapter := PrinterAdapter{
+		OldPrinter: &MyLegacyPrinter{},
+		Msg:        msg,
+	}
+	returnedMsg := adapter.PrintStored()
+	if returnedMsg != "Legacy Printer: Adapter: Hello world!!!\n" {
+		t.Errorf("Message didnt match: %s\n", returnedMsg)
+	}
+}