Gob Decoder Returning EOF Error

Question

I am attempting to implement an interface based message queue where jobs are pushed as bytes to a redis queue. But I keep receiving an EOF error when attempting to decode the byte stream.

https://play.golang.org/p/l9TBvcn9qg

Could someone point me in the right direction?

Thank you!

Answer 1

In your Go Playground example, you're trying to encode an interface and interfaces don't have a concrete implementation. If you remove the interface from your A struct, that should work. Like the following:

package main

import "fmt"
import "encoding/gob"
import "bytes"

type testInterface interface{}

type A struct {
  Name string
  Interface *B // note this change here
}

type B struct {
  Value string
}

func main() {
  var err error
  test := &A {
    Name: "wut",
    Interface: &B{Value: "BVALUE"},
  }
  buf := bytes.NewBuffer([]byte{})
  enc := gob.NewEncoder(buf)
  dec := gob.NewDecoder(buf)

  // added error checking as per Mark's comment
  err = enc.Encode(test)
  if err != nil {
    panic(err.Error())
  }

  result := &A{}
  err := dec.Decode(result)
  fmt.Printf("%+v\n", result)
  fmt.Println("Error is:", err)
  fmt.Println("Hello, playground")
}

Also, just as a side note you will see some sort of output like the following: &{Name:wut Interface:0x1040a5a0} because A is referencing a reference to a B struct. To clean that up further:

type A struct{
  Name string
  Interface B // no longer a pointer
}

func main() {
   // ...
   test := &A{Name: "wut", Interface: B{Value: "BVALUE"}}
   // ...
}

Answer 2

Found the answer to the problem from Mark above. I have forgotten to do a gob.Register(B{})

https://play.golang.org/p/7rQDHvMhD7