Golang学习数据结构和算法中文版第5篇

　　《Learn Data Structures and Algorithms with Golang》作者: Bhagvan Kommadi
　　门面(Facade)
　　门面是用来抽象子系统接口的助手。门面模式用于解决接口数量不断增加且系统变得复杂的场景。门面是不同子系统的一个入口点，它简化了系统之间的依赖关系。门面模式提供一个隐藏了代码背后实现的细节接口。
　　松散耦合原则可以通过门面模式来实现。你可以使用门面来改进设计不佳的API。在SOA里，一个服务门面可以合并对契约和实现的改变。
　　门面模式由facade类，模块类和客户端组成：门面将来自客户端的请求委托给模块类。facade 隐藏了子系统的逻辑和规则的复杂性。模块类实现模块子系统的行为和功能。客户端调用facade方法。facade类功能可以分布在多个包和程序集中。
　　例如，账户，客户和交易都是具有账户，客户和交易创建方法的类。BranchManagerFacade类被客户端用来创建账户，客户和交易：//main package has examples shown // in Hands-On Data Structures and algorithms with Go book package main // importing fmt package import (   ＂fmt＂ ) //Account struct type Account struct{   id string   accountType string } //Account class method create - creates account given AccountType func (account *Account) create(accountType string) *Account{   fmt.Println(＂account creation with type＂)   account.accountType = accountType   return account } //Account class method getById given id string func (account *Account) getById(id string) *Account {   fmt.Println(＂getting account by Id＂)   return account }
　　account类由deleteById方法，该方法用于删除带有给定ID的账户，如下面的代码所示：//Account class method deleteById given id string func (account *Account) deleteById(id string)() {   fmt.Println(＂delete account by id＂) } //Customer struct type Customer struct{   name string   id int }
　　在下面代码中，customer类有一个带name参数的创建新客户方法：//Customer class method create - create Customer given name func (customer *Customer) create(name string) *Customer {   fmt.Println(＂creating customer＂)   customer.name = name   return customer } //Transaction struct type Transaction struct{   id string   amount float32   srcAccountId string   destAccountId string }
　　正如以下代码所示，transaction类有一个create方法来创建一笔交易：//Transaction class method create Transaction func (transaction *Transaction) create(srcAccountId string, destAccountId string,amount float32) *Transaction {   fmt.Println(＂creating transaction＂)   transaction.srcAccountId = srcAccountId   transaction.destAccountId = destAccountId   transaction.amount = amount   return transaction } //BranchManagerFacade struct type BranchManagerFacade struct {   account *Account   customer *Customer   transaction *Transaction } //method NewBranchManagerFacade func NewBranchManagerFacade() *BranchManagerFacade {   return &BranchManagerFacade{ &Account{}, &Customer{}, &Transaction{}} }
　　BranchManagerFacade类有createCustomerAccount方法，此方法调用customer实例的create方法，如下代码所示：//BranchManagerFacade class method createCustomerAccount func (facade *BranchManagerFacade) createCustomerAccount(customerName string, accountType string) (*Customer,*Account) {   var customer = facade.customer.create(customerName)   var account = facade.account.create(accountType)   return customer, account } //BranchManagerFacade class method createTransaction func (facade *BranchManagerFacade) createTransaction(srcAccountId string, destAccountId string, amount float32) *Transaction {   var transaction = facade.transaction.create(srcAccountId,destAccountId,amount)   return transaction }
　　main方法调用NewBranchManagerFacade方法创建一个门面实例，调用这个facade上的方法可以创建customer和account：//main method func main() {   var facade = NewBranchManagerFacade()   var customer *Customer   var account *Account   customer, account = facade.createCustomerAccount(＂Thomas Smith＂, ＂Savings＂)   fmt.Println(customer.name)   fmt.Println(account.accountType)   var transaction = facade.createTransaction(＂21456＂,＂87345＂,1000)   fmt.Println(transaction.amount) }
　　运行以下命令：go run facade.go
　　让我们看看下一节的享元模式。
　　上一篇：《Golang学习数据结构和算法》中文版 第4篇