Go语言中的建造者模式

package main

import "fmt"

// CarBuilder is the abstract interface for car builders
type CarBuilder interface {
  SetSeats(int) CarBuilder
  SetEngine(string) CarBuilder
  SetTripComputer(bool) CarBuilder
  SetGPS(bool) CarBuilder
  GetResult() interface{}
}

// Car is the product struct for cars
type Car struct {
  seats        int
  engine       string
  tripComputer bool
  gps          bool
}

// CarManual is the product struct for car manuals
type CarManual struct {
  seats        string
  engine       string
  tripComputer string
  gps          string
}

// CarBuilderImpl is the concrete struct for car builder
type CarBuilderImpl struct {
  car *Car // the reference to the car product
}

// SetSeats is the method of CarBuilderImpl to set seats
func (c *CarBuilderImpl) SetSeats(seats int) CarBuilder {
  c.car.seats = seats // set the seats field of the car product
  return c             // return itself for chaining
}

// SetEngine is the method of CarBuilderImpl to set engine
func (c *CarBuilderImpl) SetEngine(engine string) CarBuilder {
  c.car.engine = engine // set the engine field of the car product
  return c               // return itself for chaining
}

// SetTripComputer is the method of CarBuilderImpl to set trip computer
func (c *CarBuilderImpl) SetTripComputer(tripComputer bool) CarBuilder {
  c.car.tripComputer = tripComputer // set the trip computer field of the car product
  return c                          // return itself for chaining
}

// SetGPS is the method of CarBuilderImpl to set GPS
func (c *CarBuilderImpl) SetGPS(gps bool) CarBuilder {
  c.car.gps = gps // set the GPS field of the car product
  return c         // return itself for chaining
}

// GetResult is the method of CarBuilderImpl to get the car product
func (c *CarBuilderImpl) GetResult() interface{} {
  return c.car // return the car product
}

// CarManualBuilderImpl is the concrete struct for car manual builder
type CarManualBuilderImpl struct {
  manual *CarManual // the reference to the car manual product
}

// SetSeats is the method of CarManualBuilderImpl to set seats
func (c *CarManualBuilderImpl) SetSeats(seats int) CarBuilder {
  c.manual.seats = fmt.Sprintf("The car has %d seats", seats) // set the seats field of the car manual product with some explanation
  return c                                                    // return itself for chaining
}

// SetEngine is the method of CarManualBuilderImpl to set engine
func (c *CarManualBuilderImpl) SetEngine(engine string) CarBuilder {
  c.manual.engine = fmt.Sprintf("The car has a %s engine", engine) // set the engine field of the car manual product with some explanation
  return c                                                         // return itself for chaining
}

// SetTripComputer is the method of CarManualBuilderImpl to set trip computer
func (c *CarManualBuilderImpl) SetTripComputer(tripComputer bool) CarBuilder {
  if tripComputer {
    c.manual.tripComputer = "The car has a trip computer" // set the trip computer field of the car manual product with some explanation

  } else {
    c.manual.tripComputer = "The car does not have a trip computer" // set the trip computer field of the car manual product with some explanation
  }
  return c // return itself for chaining
}

// SetGPS is the method of CarManualBuilderImpl to set GPS
func (c *CarManualBuilderImpl) SetGPS(gps bool) CarBuilder {
  if gps {
    c.manual.gps = "The car has a GPS system" // set the GPS field of the car manual product with some explanation

  } else {
    c.manual.gps = "The car does not have a GPS system" // set the GPS field of the car manual product with some explanation
  }
  return c // return itself for chaining
}

// GetResult is the method of CarManualBuilderImpl to get the car manual product
func (c *CarManualBuilderImpl) GetResult() interface{} {
  return c.manual // return the car manual product
}

func main() {
  // create a car builder and a car manual builder
  carBuilder := &CarBuilderImpl{car: &Car{}}
  carManualBuilder := &CarManualBuilderImpl{manual: &CarManual{}}

  // build a sports car and its manual
  sportsCar := carBuilder.SetSeats(2).SetEngine("V8").SetTripComputer(true).SetGPS(true).GetResult().(*Car)
  sportsCarManual := carManualBuilder.SetSeats(2).SetEngine("V8").SetTripComputer(true).SetGPS(true).GetResult().(*CarManual)

  // print the sports car and its manual
  fmt.Println("Sports Car:")
  fmt.Printf("Seats: %d\n", sportsCar.seats)
  fmt.Printf("Engine: %s\n", sportsCar.engine)
  fmt.Printf("Trip Computer: %t\n", sportsCar.tripComputer)
  fmt.Printf("GPS: %t\n", sportsCar.gps)

  fmt.Println("Sports Car Manual:")
  fmt.Printf("Seats: %s\n", sportsCarManual.seats)
  fmt.Printf("Engine: %s\n", sportsCarManual.engine)
  fmt.Printf("Trip Computer: %s\n", sportsCarManual.tripComputer)
  fmt.Printf("GPS: %s\n", sportsCarManual.gps)

  // output:
  // Sports Car:
  // Seats: 2
  // Engine: V8
  // Trip Computer: true
  // GPS: true
  // Sports Car Manual:
  // Seats: The car has 2 seats
  // Engine: The car has a V8 engine
  // Trip Computer: The car has a trip computer
  // GPS: The car has a GPS system

  // build a city car and its manual
  cityCar := carBuilder.SetSeats(4).SetEngine("V4").SetTripComputer(false).SetGPS(false).GetResult().(*Car)
  cityCarManual := carManualBuilder.SetSeats(4).SetEngine("V4").SetTripComputer(false).SetGPS(false).GetResult().(*CarManual)

  // print the city car and its manual
  fmt.Println("City Car:")
  fmt.Printf("Seats: %d\n", cityCar.seats)
  fmt.Printf("Engine: %s\n", cityCar.engine)
  fmt.Printf("Trip Computer: %t\n", cityCar.tripComputer)
  fmt.Printf("GPS: %t\n", cityCar.gps)

  fmt.Println("City Car Manual:")
  fmt.Printf("Seats: %s\n", cityCarManual.seats)
  fmt.Printf("Engine: %s\n", cityCarManual.engine)
  fmt.Printf("Trip Computer: %s\n", cityCarManual.tripComputer)
  fmt.Printf("GPS: %s\n", cityCarManual.gps)

  // output:
  // City Car:
  // Seats: 4
  // Engine: V4
  // Trip Computer: false
  // GPS: false
  // City Car Manual:
  // Seats: The car has 4 seats
  // Engine: The car has a V4 engine
  // Trip Computer: The car does not have a trip computer
  // GPS: The car does not have a GPS system

}