goavro and original Go data structure - go

Question

How can I recreate original data structure in Golang serialized with avro using goavro?
With this library https://github.com/hamba/avro it's quite easy.
out := SimpleRecord{}
err = avro.Unmarshal(schema, data, &out)
type of variable out is SimpleRecord.
Let's say I have this struct and avro schema:
type SimpleRecord struct {
F1 int `avro:"f1"`
F2 string `avro:"f2"`
F3 string `avro:"f3"`
Dependencies []string `avro:"dependencies"`
}
func main() {
avro_schema_txt := `{
"type": "record",
"name": "AvroData",
"namespace": "data.avro",
"doc": "docstring",
"fields": [
{
"name": "f1",
"type": "int"
},
{
"name": "f2",
"type": "string"
},
{
"name": "f3",
"type": "string"
},
{
"name": "dependencies",
"type": {
"type": "array",
"items": "string"
}
}
]
}`
}
and then
codec, err := goavro.NewCodec(avro_schema_txt)
if err != nil {
log.Fatal(err.Error())
}
out, _, err := codec.NativeFromBinary(data)
if err != nil {
log.Fatal(err.Error())
}
fmt.Println(out)
where data is marshaled with avro, out is of type interface{}, so how can I "make" it SimpleRecord?

Answer 1

There are two ways you can do it, either by casting out and doing a 'manual mapping' or by using codec.TextualFromNative. Both approaches are shown below for completeness,
Approach 1
Cast out from interface{} to map[string]interface{} and retrieve the values
...
simpleMap := out.(map[string]interface{})
f1 := simpleMap["f1"]
f2 := simpleMap["f2"]
...
SimpleRecord {
F1: f1,
F2: f2,
...
}
Approach 2
Use TextualFromNative, the below code shows both encode decode process
var avro_schema_txt = `{
"type": "record",
"name": "AvroData",
"namespace": "data.avro",
"doc": "docstring",
"fields": [
{
"name": "f1",
"type": "int"
},
{
"name": "f2",
"type": "string"
},
{
"name": "f3",
"type": "string"
},
{
"name": "dependencies",
"type": {
"type": "array",
"items": "string"
}
}
]
}`
// added json to match field names in avro
type SimpleRecord struct {
F1 int `avro:"f1" json:"f1"`
F2 string `avro:"f2" json:"f2"`
F3 string `avro:"f3" json:"f3"`
Dependencies []string `avro:"dependencies" json:"dependencies"`
}
func encodeDecode() {
data := SimpleRecord{
F1: 1,
F2: "tester2",
F3: "tester3",
Dependencies: []string { "tester4", "tester5" },
}
codec, err := goavro.NewCodec(avro_schema_txt)
if err != nil {
log.Fatal(err.Error())
}
// encode
textualIn, err := json2.Marshal(data)
if err != nil {
log.Fatal(err.Error())
}
nativeIn, _, err := codec.NativeFromTextual(textualIn)
if err != nil {
log.Fatal(err.Error())
}
binaryIn, err := codec.BinaryFromNative(nil, nativeIn)
if err != nil {
log.Fatal(err.Error())
}
// decode
nativeOut, _, err := codec.NativeFromBinary(binaryIn)
if err != nil {
log.Fatal(err.Error())
}
textualOut, err := codec.TextualFromNative(nil, nativeOut)
if err != nil {
log.Fatal(err.Error())
}
var out = SimpleRecord{}
err = json2.Unmarshal(textualOut, &out)
if err != nil {
log.Fatal(err.Error())
}
if !reflect.DeepEqual(data, out) {
log.Fatal("should be equal")
}
}