Serde Deserilize with keyword tag

Question

The following code snippet is how I use serde::Deserialize;

#[derive(Debug, Deserialize)]
struct OuterStruct{  
  name: String,
  value: i64,
  inner: Wrapper,
}
#[derive(Debug, Deserialize)]
struct structA{
  #[serde(rename = "type")]
  ttype: String
  field: String
}
#[derive(Debug, Deserialize)]
struct structB{
  #[serde(rename = "type")]
  ttype: String
  field: String
}
#[derive(Debug, Deserialize)]
#[serde(tag = "type")]
enum Wrapper{
  typea(structA),
  typeb(structB),
}

To my understanding the #[serde(tag = "type")] specifies the field type which decides what enum's variant to use for Deserialize.

But when I use it like that I get errors like

missing field ``type`` at line 1 column 177

I've also tried #[serde(tag = "ttype")] which is the original field name but to no avail.

My current workaround is:

Like cafce25 mentioned in the answer removing ttype from the struct. And also do

impl Wrapper{
  fn get_type(&self)->String{
    match &self{
      Wrapper::typea(_)=>"typea".to_string(),
      Wrapper::typeb(_)=>"typeb".to_string(),
    }
  }
}

Is there anyway for me to keep type field within the struct?

please provide complete example of input. – Stargateur Jan 03 '23 at 15:15 — Stargateur, Jan 03 '23 at 15:15

cafce25 · Answer 1 · 2023-01-03T13:10:49.580

The point of #[serde(tag = "type")] is to not have a redundant field on your structs since the information is encoded in the type, just remove the ttype fields from your structs.

use serde::Deserialize;
#[derive(Debug, Deserialize)]
struct StructA {
    field: String,
}
#[derive(Debug, Deserialize)]
struct StructB {
    field: String,
}
#[derive(Debug, Deserialize)]
#[serde(tag = "type")]
enum Wrapper {
    TypeA(StructA),
    TypeB(StructB),
}

Serde Deserilize with keyword tag

1 Answers1