go - 接口类型转换不起作用

Question

func GetResult (service interface{}) {
   switch v := service.(type) {
     case services.Account:
       service = service.(services.Account)
     default:
       service = service.(Mock_Account)
    }
   res, err := service.GetAccount()
 }

它说服务是接口类型没有任何方法。有类型转换不起作用任何想法如何调用 GetAccount 方法？

Answer 1

要注释您的代码示例：

func GetResult (service interface{}) {
    // service is of type interface{}
    switch v := service.(type) {
    case services.Account:
        // This does nothing: it assigns the existing value back into service, which is still of type interface{}
        // v exists in scope and is of type services.Account, but it's unused.
        service = service.(services.Account)
    default:
        // Ditto
        service = service.(Mock_Account)
    }
    // service is still of type interface{}, which defines no methods
    res, err := service.GetAccount()
}

如您所见，service这里的变量始终为interface{}. 变量的类型不能改变：Go 是静态类型的。但是，如果您只想GetAccount在传入的任何类型上调用方法，则可以在没有类型断言的情况下通过声明接口来实现完全类型安全：

type AccountGetter interface {
    GetAccount() (res ResultType, err error)
}

func GetResult(service AccountGetter) {
    res,err := service.GetAccount()
}

然后，您可以调用GetResult并传递 aservices.Account或 aMock_Account或任何实现GetAccount具有适当签名的方法的类型。