Query: Is there any method with which I can convert Value to my defined struct.

[Prince Khanna]

HI,

fastjson seems very good library which I would love to have in my project. In one of my use cases, I want to convert a value struct to my defined struct. Is there any method available in fastjson for that?

[Aliaksandr Valialkin]

Just write the corresponding function that unmarshals JSON to custom struct and use the function. For instance:

type myStruct struct {
    Foo []byte
    A []int
}

var myStructParsers fastjson.ParserPool

// Unmarshal unmarshals JSON s to ms.
func (ms *myStruct) Unmarshal(s string) {
    p := myStructParsers.Get()
    defer myStructParsers.Put(p)
    v, err := p.Parse(`{"foo": "bar", "a": [1,2,3]}`)
    if err != nil {
        return err
    }
    ms.Foo = append(ms.Foo[:0], v.GetStringBytes("foo")...)
    ms.A = ms.A[:0]
    for _, av := range v.GetArray("a") {
        ms.A = append(ms.A, av.GetInt()
    }
    return nil
}

[Prince Khanna]

Thanks man for the suggestion.

type System struct {
	SystemNumber    string  ` json:"system_number"`
	SystemID        string  `json:"system_id"`
	ExternalID      string  `json:"external_id"`
	SystemRole      string  `json:"system_role"`
	LifecycleStatus string  `json:"lifecycle_status"`
	BusinessType    string  `json:"business_type"`
	Location        *string `json:"location"`
}

systems := value.GetArray("systems")
system := test.System{}
json.Unmarshal([]byte(systems[0].String()), &system)

Payload is

{
	"replication_mode": "FULL",
	"version": "V1.0",
	"notification_id": "1",
	"systems": [
		{
			"change_mode": "U",
			"system_number": "1",
			"system_id": "1",
			"external_id": "1",
			"system_role": "1",
			"lifecycle_status": "L",
			"location": "1",
			"business_type": "1"
		}
	]
}

I am looking for some generic unmarshal which can convert json string to my struct. Ablove given unmarshal is from "encoding/json". Is there similar unmarshal present in fastjson?

[Aliaksandr Valialkin]

@princekhanna13 , fastjson doesn't provide generic unmarshaling to user-defined struct. There are no plans for adding such a functionality, since it will be slow. It should rely on Go reflection, which allocates a lot, losing performance advantage of fastjson over encoding/json.

[Prince Khanna]

Ok, I understand. I will make custom unmarshal for my structs.

Closing the issue.

Thanks.