Golang设计模式之外观模式讲解和代码示例

package main
import (
	"fmt"
)
type WalletFacade struct {
	account      *Account
	wallet       *Wallet
	securityCode *SecurityCode
	notification *Notification
	ledger       *Ledger
}
func newWalletFacade(accountID string, code int) *WalletFacade {
	fmt.Println("Starting create account")
	var walletFacade = &WalletFacade{
		account:      newAccount(accountID),
		securityCode: newSecurityCode(code),
		wallet:       newWallet(),
		notification: &Notification{},
		ledger:       &Ledger{},
	}
	fmt.Println("Account created")
	return walletFacade
}
func (w *WalletFacade) addMoneyToWallet(accountID string, securityCode int, amount int) error {
	fmt.Println("Start add money to wallet")
	err := w.account.checkAccount(accountID)
	if err != nil {
		return err
	}
	err = w.securityCode.checkCode(securityCode)
	if err != nil {
		return err
	}
	w.wallet.creditBalance(amount)
	w.notification.sendWalletCreditNotification()
	w.ledger.makeEntry(accountID, "credit", amount)
	return nil
}
func (w *WalletFacade) deductMoneyFromWallet(accountID string, securityCode, amount int) error {
	fmt.Println("Starting debit money from wallet")
	err := w.account.checkAccount(accountID)
	if err != nil {
		return err
	}
	err = w.securityCode.checkCode(securityCode)
	if err != nil {
		return err
	}
	err = w.wallet.debitBalance(amount)
	if err != nil {
		return err
	}
	w.notification.sendWalletCreditNotification()
	w.ledger.makeEntry(accountID, "debit", amount)
	return nil
}

package main
import "fmt"
type Account struct {
	name string
}
func newAccount(name string) *Account {
	return &Account{
		name: name,
	}
}
func (a *Account) checkAccount(name string) error {
	if a.name != name {
		return fmt.Errorf("Account Name is incorrect")
	}
	fmt.Println("Account Verified")
	return nil
}

package main
import "fmt"
type SecurityCode struct {
	code int
}
func newSecurityCode(code int) *SecurityCode {
	return &SecurityCode{code: code}
}
func (s *SecurityCode) checkCode(incomingCode int) error {
	if s.code != incomingCode {
		return fmt.Errorf("Security Code is incorrect")
	}
	fmt.Println("SecurityCode Verified")
	return nil
}

package main
import "fmt"
type Wallet struct {
	balance int
}
func newWallet() *Wallet {
	return &Wallet{balance: 0}
}
func (w *Wallet) creditBalance(amount int) {
	w.balance += amount
	fmt.Println("Wallet balance added successfully")
	return
}
func (w *Wallet) debitBalance(amount int) error {
	if w.balance < amount {
		return fmt.Errorf("Balance is not sufficient")
	}
	w.balance -= amount
	return nil
}

package main
import "fmt"
type Ledger struct{}
func (s *Ledger) makeEntry(accountID, txnType string, amount int) {
	fmt.Printf("Make ledger entry for accountId %s with txnType %s for amount %d\n", accountID, txnType, amount)
	return
}

package main
import "fmt"
type Notification struct{}
func (n *Notification) sendWalletCreditNotification() {
	fmt.Println("sending wallet credit notification")
}
func (n *Notification) sendWalletDebitNotification() {
	fmt.Println("Sending wallet debit notification")
}

package main
import (
	"fmt"
	"log"
)
func main() {
	fmt.Println()
	walletFacade := newWalletFacade("abc", 1234)
	fmt.Println()
	err := walletFacade.addMoneyToWallet("abc", 1234, 10)
	if err != nil {
		log.Fatalf("error: %s \n", err.Error())
	}
	fmt.Println()
	err = walletFacade.deductMoneyFromWallet("abc", 1234, 5)
	if err != nil {
		log.Fatalf("error: %s \n", err.Error())
	}
}