一、简介

代理模式（Proxy Design Pattern）在不改变原始类（或叫被代理类）代码的情况下，通过引入代理类来给原始类附加功能。

二、优点

• 关注点分离
• 访问控制
• 延迟实例化
• 远程访问
• 缓存
• 增加附加功能

三、应用场景

• 访问控制
• 缓存
• 保护代理
• 远程对象
• 智能引用
• 其他：日志记录、监控和审计等

四、UML类图

五、案例

银行提供存款和取款两种功能，不同权限的用户功能不同，只有管理权限的账号能存取款，普通用户只能存款。

package mainimport "fmt"type BankAccount interface {Deposit(amount float64)Withdraw(amount float64)
}type RealBankAccount struct {Balance float64
}func NewRealBankAccount(initialBalance float64) RealBankAccount {return RealBankAccount{Balance: initialBalance}
}func (rba *RealBankAccount) Deposit(amount float64) {rba.Balance += amountfmt.Printf("Deposited: %v, new balance: %v\n", amount, rba.Balance)
}func (rba *RealBankAccount) Withdraw(amount float64) {if rba.Balance >= amount {rba.Balance -= amountfmt.Printf("Withdrew: %v, new balance: %v\n", amount, rba.Balance)} else {fmt.Printf("Insufficient balance\n")}
}type BankAccountProxy struct {UserRole        stringRealBankAccount RealBankAccount
}func NewBankAccountProxy(userRole string, initialBalance float64) BankAccountProxy {return BankAccountProxy{UserRole: userRole, RealBankAccount: NewRealBankAccount(initialBalance)}
}func (proxy *BankAccountProxy) Deposit(amount float64) {if proxy.UserRole == "Admin" || proxy.UserRole == "User" {proxy.RealBankAccount.Deposit(amount)} else {fmt.Printf("Unauthorized access\n")}
}func (proxy *BankAccountProxy) Withdraw(amount float64) {if proxy.UserRole == "Admin" {proxy.RealBankAccount.Withdraw(amount)} else {fmt.Printf("Unauthorized access\n")}
}func main() {adminBankAccount := NewBankAccountProxy("Admin", 1000)adminBankAccount.Deposit(500)adminBankAccount.Withdraw(200)userBankAccount := NewBankAccountProxy("User", 1000)userBankAccount.Deposit(500)userBankAccount.Withdraw(200)
}