在使用过程中，如何为没有任何参数的类型创建构造函数

问题描述：

Given this type

type Response map[string]interface{}

I created a method NewResponse which fills in the default values:

 func NewResponse() Response {
    resp := Response{"status": 200, "msg": "Added jobs to queue"}

    resp_metadata := make(map[string]string)
    resp_metadata["base"] = "api/v1"
    resp_metadata["self"] = "/crawler/jobs/add"
    resp["metadata"] = resp_metadata
    return resp
}

which i call like NewResponse() but I would like to do Response.New() instead, so the method signature should be like this

func (Response) New() Response {

but then I always get the error not enough arguments in call to Response.New.

So, how could this be implemented?

给出此类型 p>

  type响应图[string]接口 {} 
  code>  pre> 
 
 我创建了一个方法NewResponse，它填充了默认值： p> 
 
 
  func NewResponse（）响应 {
 resp：=响应{“状态”：200，“ msg”：“已将作业添加到队列”} 
 
 resp_metadata：= make（map [string] string）
 resp_metadata [“ base”] =“  api / v1“ 
 resp_metadata [” self“] =” / crawler / jobs / add“ 
 resp [” metadata“] = resp_metadata 
返回resp 
} 
  code>  pre> 
  
 我称之为 NewResponse（） code>，但是我想做 Response.New（） code>，所以方法签名应该像这样 p  > 
 
 
  func（响应）New（）响应{
  code>  pre> 
 
 ，但是我总是收到错误参数不足 在对Response.New  code>的调用中。 p> 
 
 
那么，如何实现呢？   p> 
  div>

答

Although it is definitely not idiomatic Go, you could do something like this:

type Response map[string]interface{}

func (r *Response) New() {
  *r = make(map[string]interface{})
  (*r)["hello"] = "World"
  (*r)["high"] = 5
}

func main() {
  var r Response
  r.New()
  for k, v := range r {
    fmt.Printf("%s = %v
", k, v)
  }
}

But really, there's nothing wrong with func NewResponse() Response.

答

It doesn't. Go doesn't have constructors. To create an "empty" object is to create a zero value of the type of the object.

What you're trying to do is a Response method named New to be called on an existing Response object that would return a (different) Response object.

resp := Response{} or resp := make(Response) is fine if you need to create an empty Response.

答

When you write Go programs, use idiomatic Go. Then, other people will be able to read your programs. For example,

package main

import "fmt"

type Response map[string]interface{}

func NewResponse() Response {
    metadata := map[string]string{
        "base": "api/v1",
        "self": "/crawler/jobs/add",
    }
    r := Response{
        "status":   200,
        "msg":      "Added jobs to queue",
        "metadata": metadata,
    }
    return r
}

func main() {
    resp := NewResponse()
    fmt.Println(resp)
}

Output:

map[status:200 msg:Added jobs to queue metadata:map[base:api/v1 self:/crawler/jobs/add]]

在使用过程中，如何为没有任何参数的类型创建构造函数

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