Golang将接口{}转换为struct

Question

我想在下面的代码中改进getCustomerFromDTO方法，我需要从interface {}创建一个结构，目前我需要将该接口编组为byte
[]，然后将数组解组为我的结构-必须有更好的方法。

我的用例是，我通过rabbitmq发送结构，然后使用具有其他特定于域的数据的通用DTO包装器来发送它们。当我从Rabbit
MQ接收DTO时，消息下方的一层将被封送给我的DTO，然后我需要从该DTO获取我的结构。

type Customer struct {
    Name string `json:"name"`
}

type UniversalDTO struct {
    Data interface{} `json:"data"`
    // more fields with important meta-data about the message...
}

func main() {
    // create a customer, add it to DTO object and marshal it
    customer := Customer{Name: "Ben"}
    dtoToSend := UniversalDTO{customer}
    byteData, _ := json.Marshal(dtoToSend)

    // unmarshal it (usually after receiving bytes from somewhere)
    receivedDTO := UniversalDTO{}
    json.Unmarshal(byteData, &receivedDTO)

    //Attempt to unmarshall our customer
    receivedCustomer := getCustomerFromDTO(receivedDTO.Data)
    fmt.Println(receivedCustomer)
}

func getCustomerFromDTO(data interface{}) Customer {
    customer := Customer{}
    bodyBytes, _ := json.Marshal(data)
    json.Unmarshal(bodyBytes, &customer)
    return customer
}

Answer 1

解组DTO之前，请将Data字段设置为所需的类型。

type Customer struct {
    Name string `json:"name"`
}

type UniversalDTO struct {
    Data interface{} `json:"data"`
    // more fields with important meta-data about the message...
}

func main() {
    // create a customer, add it to DTO object and marshal it
    customer := Customer{Name: "Ben"}
    dtoToSend := UniversalDTO{customer}
    byteData, _ := json.Marshal(dtoToSend)

    // unmarshal it (usually after receiving bytes from somewhere)
    receivedCustomer := &Customer{}
    receivedDTO := UniversalDTO{Data: receivedCustomer}
    json.Unmarshal(byteData, &receivedDTO)

    //done
    fmt.Println(receivedCustomer)
}

如果您无法Data在解组前在DTO上初始化字段，则可以在解组后使用类型断言。encoding/json将interface{}类型值unamrshals
打包到中map[string]interface{}，因此您的代码将如下所示：

type Customer struct {
    Name string `json:"name"`
}

type UniversalDTO struct {
    Data interface{} `json:"data"`
    // more fields with important meta-data about the message...
}

func main() {
    // create a customer, add it to DTO object and marshal it
    customer := Customer{Name: "Ben"}
    dtoToSend := UniversalDTO{customer}
    byteData, _ := json.Marshal(dtoToSend)

    // unmarshal it (usually after receiving bytes from somewhere)
    receivedDTO := UniversalDTO{}
    json.Unmarshal(byteData, &receivedDTO)

    //Attempt to unmarshall our customer
    receivedCustomer := getCustomerFromDTO(receivedDTO.Data)
    fmt.Println(receivedCustomer)
}

func getCustomerFromDTO(data interface{}) Customer {
    m := data.(map[string]interface{})
    customer := Customer{}
    if name, ok := m["name"].(string); ok {
        customer.Name = name
    }
    return customer
}