Typecast between anonymous structs with field tags

user_2011051 0
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I had an Open API generated schema, and I would like to create the response struct in my handler function. But when I want to create the anonymous struct, I need to write again the field tags, too. Is there any solution for not needing to repeat that? Here is the minimal example

package main

// Response is generated by a tool in a separated file
type Response struct {
    Result *struct {
        Id int `json:"id"`
    } `json:"result,omitempty"`
}

func main() {
    var response Response

    response.Result = &struct {
        Id int `json:"id"`
    }{5}

    // This results in an error
    // cannot use &struct { Id int } literal (type *struct { Id int }) as type *struct { Id int "json:\"id\"" } in assignment
    response.Result = &struct {Id int}{5}
}

This anonymous struct is a result of oapi-codegen, when I use a complex type in the components part of the api definition as a response type. I think if I use a CreateBookResponseResult type, the code generator won't generate an anonymous struct, but I would postpone this option until I can.

components:
  CreateBookResponse:
    type: object
    properties:
      result:
        type: object
        properties:
          id:
            type: integer
go
1 Answers

Use a named type.

type Response struct {
    Result *ResponseResult `json:"result,omitempty"`
}

type ResponseResult struct {
        Id int `json:"id"`
} 


var response Response
response.Result = &ResponseResult{Id: 5}
user_136670870
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