Behavioral - Chain of Responsibility

behavioral/chain_of_responsibility.md

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+# Observer Pattern
+
+The [chain of responsibility pattern](https://en.wikipedia.org/wiki/Chain-of-responsibility_pattern) is a design pattern consisting in a series of independent processes that will run in in sequence. It gives power to rearange the sequence or add new processes at the end of it without changing its structure.
+
+## Implementation
+
+Each process in the chain must implement a function to be executed and call the next process at the end.
+It will call each process recursivelly until there is no more porcesses in the chain of responsibility.
+
+## Usage
+
+For usage, see [chain_of_responsibility/main.go](chain_of_responsibility/main.go) or [view in the Playground](https://play.golang.org/p/XA2v0XlenAi).

behavioral/chain_of_responsibility/main.go

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+package main
+
+import "fmt"
+
+type task interface {
+	execute()
+	setNext(task)
+}
+
+type turnOnLights struct {
+	next task
+}
+
+func (turnOnLights *turnOnLights) execute() {
+	fmt.Println("Turning the lights on...")
+	if turnOnLights.next != nil {
+		turnOnLights.next.execute()
+	}
+}
+
+func (turnOnLights *turnOnLights) setNext(next task) {
+	turnOnLights.next = next
+}
+
+type turnOnComputer struct {
+	next task
+}
+
+func (turnOnComputer *turnOnComputer) execute() {
+	fmt.Println("Turning the computer on...")
+	if turnOnComputer.next != nil {
+		turnOnComputer.next.execute()
+	}
+}
+
+func (turnOnComputer *turnOnComputer) setNext(next task) {
+	turnOnComputer.next = next
+}
+
+type openCodeEditor struct {
+	next task
+}
+
+func (openCodeEditor *openCodeEditor) execute() {
+	fmt.Println("Opening the code editor...")
+	if openCodeEditor.next != nil {
+		openCodeEditor.next.execute()
+	}
+}
+
+func (openCodeEditor *openCodeEditor) setNext(next task) {
+	openCodeEditor.next = next
+}
+
+type code struct {
+	next task
+}
+
+func (code *code) execute() {
+	fmt.Println("Start coding in go...")
+	if code.next != nil {
+		code.next.execute()
+	}
+}
+
+func (code *code) setNext(next task) {
+	code.next = next
+}
+
+func main() {
+	turnOnLights := &turnOnLights{}
+	turnOnComputer := &turnOnComputer{}
+	openCodeEditor := &openCodeEditor{}
+	code := &code{}
+
+	turnOnLights.setNext(turnOnComputer)
+	turnOnComputer.setNext(openCodeEditor)
+	openCodeEditor.setNext(code)
+
+	turnOnLights.execute()
+	// Out:
+	// Turning the lights on...
+	// Turning the computer on...
+	// Opening the code editor...
+	// Start coding in go...
+
+	openCodeEditor.execute()
+	// Out:
+	// Opening the code editor...
+	// Start coding in go...
+}