Merge 69c323be3c into f978e42036

behavioral/chain_of_responsibility.md

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+# Chain of responsibility
+
+The [Chain of responsibility](https://en.wikipedia.org/wiki/Chain-of-responsibility_pattern) pattern is a design pattern consisting of a source of command objects and a series of processing objects. Each processing object contains logic that defines the types of command objects that it can handle; the rest are passed to the next processing object in the chain.
+
+#implementation
+
+An example showing implementation and usage can be found in [main.go](chain_of_responsibility/main.go).

behavioral/chain_of_responsibility/main.go

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+// Package main serves as an example application that makes use of the chain of responsibility pattern.
+package main
+
+import (
+	"fmt"
+)
+
+type request struct {
+	value float64
+}
+
+//NumberProcessor has the processor method which will tell if the value is negative, positive or zero
+type NumberProcessor interface {
+	process(request)
+}
+
+//ZeroHandler handles the value which is zero
+type ZeroHandler struct {
+	numberProcessor NumberProcessor
+}
+
+//PositiveHandler handles the value which is positive
+type PositiveHandler struct {
+	numberProcessor NumberProcessor
+}
+
+//NegativeHandler handles the value which is negative
+type NegativeHandler struct {
+	numberProcessor NumberProcessor
+}
+
+//For returning zero if the value is zero.
+func (zero ZeroHandler) process(req request) {
+
+	if req.value == 0.0 {
+		fmt.Print("its zero")
+	} else {
+		zero.numberProcessor.process(req)
+	}
+}
+
+//For returning its negative if the value is negative.
+func (negative NegativeHandler) process(req request) {
+	if req.value < 0 {
+		fmt.Print("its a negative number")
+	} else {
+		negative.numberProcessor.process(req)
+	}
+}
+
+//For returning its positive if the value is positive.
+func (positve PositiveHandler) process(req request) {
+	if req.value > 0 {
+		fmt.Print("its a postitive number")
+	}
+}
+
+func main() {
+	//initialising the chain of actions.
+	zeroHandler := ZeroHandler{NegativeHandler{PositiveHandler{}}}
+
+	zeroHandler.process(request{10})
+	zeroHandler.process(request{-19.9})
+	zeroHandler.process(request{0})
+}