From 9651c9747d856c1504c2fcd4c099a35f9943ee14 Mon Sep 17 00:00:00 2001
From: Jian Han <jianhan@mail.com>
Date: Wed, 10 Jan 2018 21:42:52 +1000
Subject: [PATCH] added builder pattern

---
 .../concurrent_pattern/pipeline/main.go       | 67 +++++++++++++++
 .../creational/builder/main.go                | 84 +++++++++++++++++++
 .../creational/builder/main_test.go           | 24 ++++++
 3 files changed, 175 insertions(+)
 create mode 100644 go_design_pattern_book/concurrent_pattern/pipeline/main.go
 create mode 100644 go_design_pattern_book/creational/builder/main.go
 create mode 100644 go_design_pattern_book/creational/builder/main_test.go

diff --git a/go_design_pattern_book/concurrent_pattern/pipeline/main.go b/go_design_pattern_book/concurrent_pattern/pipeline/main.go
new file mode 100644
index 0000000..cff129c
--- /dev/null
+++ b/go_design_pattern_book/concurrent_pattern/pipeline/main.go
@@ -0,0 +1,67 @@
+package main
+
+import (
+	"fmt"
+	"sync"
+)
+
+func main() {
+	in := gen(2, 3)
+
+	// Distribute the sq work across two goroutines that both read from in.
+	c1 := sq(in)
+	c2 := sq(in)
+
+	// Consume the merged output from c1 and c2.
+	for n := range merge(c1, c2) {
+		fmt.Println(n) // 4 then 9, or 9 then 4
+	}
+}
+
+func gen(nums ...int) <-chan int {
+	out := make(chan int, len(nums))
+	go func() {
+		for _, n := range nums {
+			out <- n
+		}
+		close(out)
+	}()
+	return out
+}
+
+func sq(in <-chan int) <-chan int {
+	out := make(chan int)
+	go func() {
+		for n := range in {
+			out <- n * n
+		}
+		close(out)
+	}()
+	return out
+}
+
+func merge(cs ...<-chan int) <-chan int {
+	var wg sync.WaitGroup
+	out := make(chan int, 1) // enough space for the unread inputs
+
+	// Start an output goroutine for each input channel in cs.  output
+	// copies values from c to out until c is closed, then calls wg.Done.
+	output := func(c <-chan int) {
+		for n := range c {
+			out <- n
+		}
+		wg.Done()
+	}
+	wg.Add(len(cs))
+	for _, c := range cs {
+		go output(c)
+	}
+
+	// Start a goroutine to close out once all the output goroutines are
+	// done.  This must start after the wg.Add call.
+	go func() {
+		wg.Wait()
+		close(out)
+	}()
+	return out
+}
diff --git a/go_design_pattern_book/creational/builder/main.go b/go_design_pattern_book/creational/builder/main.go
new file mode 100644
index 0000000..75969b1
--- /dev/null
+++ b/go_design_pattern_book/creational/builder/main.go
@@ -0,0 +1,84 @@
+package main
+
+// Builder design pattern tried to
+// 1. Abstract complex creations so that object creation is seperated from object user.
+// 2. Create an object step by step by filling it's fields and creating embedded objects.
+// 3. Reuse the object creation algorithm between many objects.
+// Builder design pattern is often described as a relationship between a director and builders.
+// Director in charge of construction of objects.
+// Builders are the ones that return actual products.
+
+// BuildProcess is a procceding interface defines each steps needed for building vehicle.
+type BuildProcess interface {
+	SetWheels() BuildProcess
+	SetSeats() BuildProcess
+	SetStructure() BuildProcess
+	GetVehicle() VehicleProduct
+}
+
+// VehicleProduct is the product that we want to retrieve while using manufacturing.
+type VehicleProduct struct {
+	Wheels    int
+	Seats     int
+	Structure string
+}
+
+// ManufacturingDirector is the one that in charge of accepting builders.
+// It has a Construct method that will use builder that is stored in Manufacturing, and will reproduce the required steps.
+type ManufacturingDirector struct {
+	builder BuildProcess
+}
+
+func (f *ManufacturingDirector) Construct() {
+	f.builder.SetSeats().SetStructure().SetWheels()
+}
+
+func (f *ManufacturingDirector) SetBuilder(b BuildProcess) {
+	f.builder = b
+}
+
+type CarBuilder struct {
+	v VehicleProduct
+}
+
+func (c *CarBuilder) SetWheels() BuildProcess {
+	c.v.Wheels = 4
+	return c
+}
+
+func (c *CarBuilder) SetSeats() BuildProcess {
+	c.v.Seats = 5
+	return c
+}
+
+func (c *CarBuilder) SetStructure() BuildProcess {
+	c.v.Structure = "Car"
+	return c
+}
+
+func (c *CarBuilder) GetVehicle() VehicleProduct {
+	return c.v
+}
+
+type BikeBuilder struct {
+	v VehicleProduct
+}
+
+func (b *BikeBuilder) SetWheels() BuildProcess {
+	b.v.Wheels = 2
+	return b
+}
+
+func (b *BikeBuilder) SetSeats() BuildProcess {
+	b.v.Seats = 2
+	return b
+}
+
+func (b *BikeBuilder) SetStructure() BuildProcess {
+	b.v.Structure = "Bike"
+	return b
+}
+
+func (b *BikeBuilder) GetVehicle() VehicleProduct {
+	return b.v
+}
diff --git a/go_design_pattern_book/creational/builder/main_test.go b/go_design_pattern_book/creational/builder/main_test.go
new file mode 100644
index 0000000..37d6a5e
--- /dev/null
+++ b/go_design_pattern_book/creational/builder/main_test.go
@@ -0,0 +1,24 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestBuilderPatter(t *testing.T) {
+	manufacturingComplex := ManufacturingDirector{}
+	carBuilder := &CarBuilder{}
+	manufacturingComplex.SetBuilder(carBuilder)
+	manufacturingComplex.Construct()
+	car := carBuilder.GetVehicle()
+	if car.Wheels != 4 {
+		t.Errorf("number of wheels in car should be 4, it is %d", car.Seats)
+	}
+
+	bikeBuilder := &BikeBuilder{}
+	manufacturingComplex.SetBuilder(bikeBuilder)
+	manufacturingComplex.Construct()
+	bike := bikeBuilder.GetVehicle()
+	if bike.Wheels != 2 {
+		t.Errorf("number of wheels on bike should be 2, it is %d", bike.Seats)
+	}
+}